K-12 GRADE 8 SCIENCE

FIRST QUARTER/FIRST GRADING PERIOD 

June 2,2015

Unit I: Forces and Motion

I. Do forces always result in motion? Forces don't just result in motion. There are other things forces can do like stop, accelerate, or even change a motion's direction. A force can give energy to an object causing the object to start moving, stop moving, or change its motion. Forces occur in pairs and can be either balanced or unbalanced. Balanced forces do not cause a change in motion. They are equal in size and opposite in direction.

Consider a ball on top of a flat surface. If you push the ball across the surface, the ball will continuously roll away. If you push the ball again in the same direction, the ball will accelerate. But if yo push the ball in the opposite direction, the ball will stop. If you push the ball different from its original position and not in the opposite direction, the ball will change its direction.


Force - Objects can be moved by either pushing or pulling, this is referred to as force.

• Balanced Force- Force acting equally on Magnitude and Line of action.

• Unbalanced Force: Forces acting unequally on Magnitude and Line of Action.

• Combined Force: Balanced + Unbalanced forces = Frictional force

• Combined Force: Gravitational Force + Tension = Magnitude

  - to accurately measure the force acting on an object is needed to be familiar with.

• Magnitude: Referred to size and strength of an object.

• Direction: Relative Magnitude of the force.

• Line of Action: Doubled force parallel to the force direction.

• Point of Application: Applied Force. 

Balanced and Unbalanced force:

An object may be acted upon by several forces. An example is an object being pushed or pulled in different directions. To identify which force would be able to change an object's motion, you need to identify which force is acting on it. To accurately describe the forces acting on an object, it is important to familiarize these terms:

• Magnitude: Refers to the size and strength of an object.

• Direction: Describes both how fast something is moving and in what direction it is moving.

• Point of application: Point of application can affect forces such as torque and momentum.

• Line of Action: is a geometric representation of how the force is applied.

 So what are balanced and unbalanced forces exactly?

An object could be acted upon by several forces. But there are two main forces that can act on it. These are balanced and unbalanced force. Balanced forces are unit of forces that will act on an object at rest causing the object to remain still. Unbalanced force are the forces that will cause the object to move and change it's velocity.



Activity I: Forces on objects at rest

Objectives: 

After performing this activity you should be able to identify the 
forces acting on objects at rest.

• A pen is hanging on a piece of string is at rest, so it's balanced. The balanced forces(including gravitational) acting on the pen causes the pen to be stable.

• String <- Pen -> Gravity

• The picture shows that the pen is acted by the balanced force of the string and gravity.

• If you cut the string, the pen will fall to the ground because gravity turns into an unstable and unbalanced force since there is no opposite reaction strong enough to counter act gravitational force.

• Pen -> -> Gravity 

• A book on top of a table is at rest since there is no unbalanced force strong enough to make it move. Now we all know that if the book is pushed by an external net or unbalanced force, the book will move.

• But the book will not move if it's counter acted by an equal force causing an unbalanced force to be equal like in this example.

• Balanced Force -> Book <- Balanced Force

June 9,2015


Activity II: Balance of forces
After performing this activity, you should be able to:
1. examine the conditions when two forces balance, and

2. explain the effect of balanced forces on the state of motion of an object.

• If a cardboard is attached to four strings on each side and it's pulled away by the strings at the same time, the cardboard will not move or even rotate when it's released.

String

           ^            

String <- Cardboard -> String

                 v                              

               String               

• The example explains that if balanced forces pull out an object with the same amount of magnitude and time, the object won't move when pulled or released.

Unbalanced Forces

 -If you cut a string connected to a pen, the pen will fall. Or if you push a book one side across the table will not continue moving unless if you continue pushing it. The pen falls because there is no more force to counteract the force of gravity. The book moves because you are applying force to it. In other words, forces are no longer balanced. If an object is initially under at rest in an unbalanced force, it will go to the direction of the unbalanced force. But how will unbalanced force affect motion?

Place a ball on the desk and gently push it to one side. Observe
the motion as rolls down the desk. Eventually ball will stop because of frictional force. Again due to the unbalanced force, the object will change its velocity.  


Combining Forces:

When we combine or add forces to determine the net or unbalanced force, we will limit our discussion to those forces which act along the same line of action. The algebraic signs + and – are used to indicate the direction of forces. Unlike signs are used for forces acting in opposite directions, like in the case of the book lying on the table. The force of gravity (Fg) and normal force (Fn) are assigned opposite signs (-Fn) is given a positive (+) sign while (Fg) is given a negative (-) sign. If both Fg and Fn are given a magnitude value of 3 units, then the net force along this line (vertical) will be:

Fnet = Fn + Fg
     = 3 units + (-3 units)
     = 0

If the sum of the forces equate to zero, they are considered balanced. If the algebraic sum is not equal to zero, the forces are unbalanced. The non-zero sum is the net or unbalanced force. This unbalanced or net force would cause a change in a body’s state of motion. 

Concept Check:

• Two net forces are pulling an object in one direction at the same time with ten units each. The net force acting on it will be 20 units since the force only goes in one direction.

• Fnet = Fn + Fg
       = 10 units + 10 units
       = 20 units

• Object->> Net Force(20)

• If two net forces are pulling an object on opposite directions with 10 units on side and 5 units on the other, the object will move to side with more units. The side where the stronger units are could move the object and bring the weaker unit along with it.

• Fnet = Fn + Fg
       = 10 units + (-5 units)
       = 5 units

• Net Force (10) <<- Object -> Net Force (5)

• If three net forces are pulling an object on opposite directions with 10 units on side and two five-unit forces on the other, the object will not move because Their net forces are the same.

• Fnet = Fn + Fg
       = 10 units + 5 units + 5 units
       = 20 units

• Net Force (10) <- Object ->> Net Force [5*2]

Newton’s Three Laws of Motion
The principles behind Newton’s laws of motion are very significant in understanding the motion of objects in our universe. Their applications are all around us. Understanding these laws therefore helps us understand why the things around us move or behave the way they do.

Newtons first law of motion: Law of inertia

Newton's first law states that an object at rest will stay at rest or an object in motion will stay in motion and travel in straight line, as long as no external net force acts on it. The object will change its state of motion only if there is unbalanced or net force acting upon it. A body will remain at rest or move at constant velocity unless acted upon by an external net or unbalanced force.


Investigating Inertia:

•  If you put a cardboard on top of a cup and a coin on top of the card board and pull it the cardboard slowly away from the cup, the coin will not fall instead it will remain on top of the cardboard. But if you pull the cardboard quickly away from the cup, the coin will fall into the cup. 

<-Coin->

->> Cardboard ->>

<-Cup->

The examples above demonstrate the property of an object to resist any change in its state of motion. In physics, this property is known as inertia. The coin dropped into the glass because it was trying to remain in its state of rest.

06/16/15

Measure of Inertia:


All objects have the tendency to resist changes in their state of motion or keep doing what they are doing. However, changing a body’s state of motion depends on its inertia. A more massive object which has more inertia is more difficult to move from rest, slow down, speed up, or change its direction.

Newton's first law states that an object at rest will stay at rest or an object in motion will stay in motion and travel in straight line, as long as no external net force acts on it. The object will change its state of motion only if there is unbalanced or net force acting upon it.

A body will remain at rest or move at constant velocity unless acted upon by an external net or unbalanced force.


Newton's Second Law of Motion: Law of Acceleration

Activity 4: Force and Acceleration 

Objectives:

After this activity you should be able to determine how the net force affects acceleration.

Procedure:

Consider the situation below:

If a group of students are conducting an experiment to determine the relationships between acceleration and the effect of a net force. They used rubber bands to pull a cart and determine the time ad distance it covered. They used tape charts to measure each distance covered and they marked each tape with dots to observe time intervals. They marked each chart to determine the force and acceleration to cart with F=1,F=2,F=3 and F=14.

A. Tape chart analysis:

• Assume that you obtained a copy of the tape charts produced by the students for the four runs:

• If you compare the charts, you will see that the lines and dots of each strip varies because length of strip in each chart represents the total distance traveled by the cart over a time interval of 0.10  seconds. Recall that the total distance traveled over a unit time gives the average  velocity  of the moving  body, or speed when traveling in straight line. Hence, each strip represents the average velocity of the cart over a time interval of 0.10 seconds. 

• Upon examining the tape chart for F=1 unit:

• You can see the increase of the strips' length that suggest about the cart's change of motion and non-uniform movement as well as the distance and time covered by the cart which is also probably true for the other runs.

• You can compare one tape to another, you can tell the change of velocity by comparing the length of the strips and the quantity of the dots marked along with it. You can see that the tape chart that shows the greatest increase in the length of the strips is chart F=5 because the force represented by the tape shows a force of 5 units.

• If you draw a line along the dots in the strips, you can see that there are different patterns formed by the line.

• You can also use the tape chart to compute for the average velocity, change in velocity (∆v), and acceleration (a) of the cart for each run.

• Each length of the strips is equal to 2.5 cm and the time interval is 0.10 seconds. You can compute the velocity by dividing the distance by the time interval.

• Velocity = Distance/time

• 25cm/s = 2.5cm/0.10sec

06.23.15

• The values of the velocity of the cart is changing, it shows that the motion of the cart is increasingly changing. The cart will not have the same movement speed if it's doubled every time the cart moves again.

• If you compare the top chart, you will see that each chart has different measures that shows changing movement speed. 

• The computed values of the tape chart have increasing acceleration.

• Observe the tape charts:

• F=1 Unit

• 1.9 cm/sec interval

• F=2 Unit

• 2.1 cm/sec interval 

• F=3 Unit

• 2.3 cm/sec interval 

• F=4 Unit

• 2.6 cm/sec interval   

A constant net force acting on an object can change his velocity at a constant rate over time. Hence, it moves when a net force is doubled, so does acceleration. A acceleration is directly proportional to the net force acting on it and inverse to it's mass.

Free-fall and Newton's second Law of Motion

Consider a situation where there are two books falling at the same height and at the same time. The two books would surprisingly reach the ground at the same time, the reason is that gravity affects all objects on the surface of the earth and causes them to accelerate when released. The acceleration is 9.8m/s every one second  due to gravity G that is the same for all  objects.

Uniform Circular Motion and Newton's second Law of Motion

Acceleration doesn't always refer to speed. It also refer to change of direction and velocity. In the case of acceleration, the changing velocity pulls the object to the center in a uniform circular path. The object gathers energy but movement still stays uniform until the changing velocity is cut off or moved. Pretty much like a thread and rock attached together while spinning around then the thread is released or cut.

06.30.15

Activity 5:
Action Reaction:
Activity 5: In this activity,you should be able to identify the comparison of two interacting forces in terms of magnitude and direction.

Procedure:

1. Connect two spring balances their hooks then ask someone two hold one end of the spring while your partner does nothing.

1. You can see that if you pull the spring balance, you will find out that you can exert force that will represent less than or equal to 32.

1. Pull the spring without exceeding to maximum.

1. Your reading would be more likely between 0 to 31.

1. Attach one end of the spring balance to the wall and and the other end to another spring balance then pull.

1. You will see that the balance spring readings are doubled even if the force you exert stays the same. 

Force ins't just something that anything exerts. Force is also a mutual interaction between two things. Like a hammer transferring its force to the nail in order to drive it into the wooden board.

• Action-Reaction and Balance Force have many similarities and few differences:
• They both have equal forces.
• They both have the same line of action.
• Action-Reaction force acts on another object.
• Balanced force react on the same object.

07.07.15
Newton's third law of motion: law of interaction

Action Reaction: In newton's third law, explains that if you apply force to an object will result an equal reaction and go to the opposite direction. Unlike balanced forces, action-reaction forces are expressed in different masses.

• Example: if you push block and exert a net force of 5 newtons, you will eventually come up with an equal reaction of also 5 newtons.

• Net force -> Object <- Reaction       

The forces of two bodies are always equal and in opposite direction.



07.21.15

Unit 2: Work and Energy
You may have utilized Newtons laws to Newtons laws to analyze the motion of objects in Module 1. This module will allow you to investigate the perspective of work and energy.

What is work?
You have learned that force can change the state of motion of an object. Work in science, doesn't mean a job or employment. It refers to the action of the body to cause a displacement. Work is done if accompanied by energy. Work gains energy if it's done on an object and loses it if it's done by an object. Work is the use of energy to move at a certain distance. The exerted force must be relative to it's direction. Work can be done if you push or pull an object since it's relative force and direction are calculated to result joules.

• Work is done If you push an object to the same course of motion as your force.

• Work isn't done If you push/pull an object and it doesn't move.

• Work isn't done If you carry an object to a different course of motion unlike your direction of force.

Activity 1: When is work done?



Objective: After performing this activity, you should be able to
explain if work is done in situations represented.




Procedure: Tell whether the situation represents work and on which object work is done.

1. A girl pulling a cart.

1. Work is done on the cart, because the direction of force is relative to the course of direction.

1. A man lifting a box upwards.

1. Work is done on the box, because the upward direction of force is relative to the upward course of direction. 

1. A woman walking while carrying a purse.

1. Work isn't done on the bag, because the direction of force isn't relative to the course of direction. 

1. A fruit falling from a tree.

1. Work is done on the fruit, because the direction of gravitational force is relative to the course of direction.  

Calculating Work:
  Work is calculate either by the amount of force applied that causes motion on an object or multiplied by mass, constant gravitational force and height. The result comes in the unit of joules. Joule is named from an English physicist James Prescott Joule, they are the result of one Newton moved to one meter.

Example:

Work = Force x Distance

3500j = 500N * 7m

Joules = Mass x Gravitational Force x Height

19.6j = 1kg * 9.8m/s^2 * 2m

* MGH is used if the given is either mass, gravitational force, height.*

07/28/15


Work and Energy


Work - Energy transferred by a force
Energy - Ability to do work


In calculating work you should remember that:

• Work = Force x Distance
• This is applied when force and distance is given

Example:

Push a block for 7m with a force of 10n. How much work is done?

Force(10n)->Block->Distance(7 meters)

Work = Force x Distance 

Work = Force(10n) x Distance(7m)

Work = 70 joules(one joule equals one Newton-meter)

Velocity of Work

Work velocity = v^F^2 = v^I^2 + 2a*d

• Work velocity + Kinetic Energy
• F*D x 1/2 m*v^2
• Example
• 5kg->7m/s
• 21437.5

Work Calculation II:

• Work = m*g*h
• F*D  = m*g*h

Example:

Work = 10kg x 9.8m/s * 100m

Work = 9800 joules

Kinetic and Potential energy

Kinetic - Moving Energy = 1/2 mv^2

Potential - Stored energy = m*g*h

Example: Kinetic Energy

• Force[10n] -> mass[450g] -> Velocity[25 m/s]; How far does the object with a mass of 450g force go if you push it with a force of 10 newtons and moves with a speed of 25m/s.
• Kinetic Energy = KE1 + KE2 = F x D
• Kinetic Energy = 1/2 x 450/1000 x (25)^2 = 10d 
• Kinetic Energy = 140.625/10
• Kinetic Energy = 14.06m

• Mass[1500] -> Speed[10m/s]; What if an object moves at 10m/s per second. How much force does it need to push the object.
• Kinetic Energy = 1/2 mv^2
• Kinetic Energy = 1/2 x 450/1000 (19)^2 
• Kinetic Energy = 75000j

• Mass[200g] -> speed[5m/s] -> Mass[300g] -> speed[4m/s]; What if an object moves with the speed of 5m/s and a mass of 200g hits an object with the mass of 300g and then moves with the speed of speed of 4m/s.
• Kinetic Energy = 1/2(200/1000)(5)^2 + 1/2(300/1000)(4)^2
• Kinetic Energy = 2.5j
• Kinetic Energy = 1/2(200/1000)(4)^2 + 1/2(300/1000)(0)^2
• Kinetic Energy = 2.4j(Loss of 0.1 Joule)     

 

08/04/15

Work is a Method of Transferring energy
 Energy in different ways can be transferred from ways can be transferred from one place to another. One of those ways is called work.
Do This:

• Play a bowling game by rolling a ball towards an empty plastic bottle.
• Is there work done?
• What can the moving ball do?

 Work is done on the ball, the energy stored in the ball causes it to move. The ball's stored energy transfers into the bottle when the ball hits it. So in conclusion, energy is the ability to do work.

Kinetic Energy:
The energy of a moving object is called energy of motion or
kinetic energy(KE). The word kinetic comes from the Greek word
kinetikos which means moving. Kinetic energy quantifies the  amount of work the object can do because of its motion.

The plastic or rubber ball you pushed to hit an empty plastic bottle earlier has kinetic energy. The force applied caused the ball to accelerate from rest to a certain velocity (v). In Module 1, you learn that acceleration is the rate of change in velocity.
In the equation: 

• a = v-v^i
• where (v) is the final velocity, (i) is the initial velocity and (t) is the time. Since the ball started from  rest, the initial velocity is zero. Thus, the acceleration is:
• a = v/t
• Substituting this in Newton’s second law: F = m*a

• The equation in finding the average velocity of the ball is: v = v^i + v^f/2

Kinetic - Moving Energy = 1/2 mv^2

Potential - Stored energy = m*g*h

Example: Kinetic Energy

• Force[10n] -> mass[450g] -> Velocity[25 m/s]; How far does the object with a mass of 450g force go if you push it with a force of 10 newtons and moves with a speed of 25m/s.
• Kinetic Energy = KE1 + KE2 = F x D
• Kinetic Energy = 1/2 x 450/1000 x (25)^2 = 10d 
• Kinetic Energy = 140.625/10
• Kinetic Energy = 14.06m

• Mass[1500] -> Speed[10m/s]; What if an object moves at 10m/s per second. How much force does it need to push the object.
• Kinetic Energy = 1/2 mv^2
• Kinetic Energy = 1/2 x 450/1000 (19)^2 
• Kinetic Energy = 75000j

• Mass[200g] -> speed[5m/s] -> Mass[300g] -> speed[4m/s]; What if an object moves with the speed of 5m/s and a mass of 200g hits an object with the mass of 300g and then moves with the speed of speed of 4m/s.
• Kinetic Energy = 1/2(200/1000)(5)^2 + 1/2(300/1000)(4)^2
• Kinetic Energy = 2.5j
• Kinetic Energy = 1/2(200/1000)(4)^2 + 1/2(300/1000)(0)^2
• Kinetic Energy = 2.4j(Loss of 0.1 Joule)     

08/11/15

Potential Energy
 Picture a man lifting a box upwards. Who is doing work? The man? The box? It's the man of course! He exerted an upward force which is equivalent to the upward direction of motion. As discussed previously, work is a way to transfer energy. First, work is done on the box, it gained energy while the man lifting it loses energy. The energy gained and lost is called potential energy.

Example:

• A book weighing 1.0kg is lifted 0.5m from the ground with a force equal to it's weight
• The acceleration due to gravity is a constant 9.8km^2
• This shows that the work done on the object is equal to the potential energy it gained.
• The potential energy it gained lifted is:
• 1kg * 9.8ms^2 * 0.5m = 4.9J 

Gravitational Potential Energy

  The potential energy gained and lost by an object is dependent on the reference level. If the same book is held 1m above the table, the potential energy gained by the book is 9.8J with the reference level of 14.7J. If the reference level is on the chair then, it's 19.6J. If the book was released from a height of 2m, the reference point reaches 9.8J then continues to fall and reach a reference point of 14.7J and reaches the ground with a reference point of 19.6J
 

Try solving this:
If the same 1.0 kg book is lifted to 0.5 m above the table, but the table top is 1.0 m above the floor, what would be the potential energy of the book if the reference level
were the floor?

• PE = mgh
• PE = 1.0 * 9.8 * 1.5
• PE = 14.7J

08.18.15

Activity 2: Rolling Toy 

1. Prepare a simple toy made of a can or plastic container.
1. 
2. After the activity, study the toy's mechanisms and and ask yourself how the energy was transferred and what kind of energy is transferred when it moves.

• Q1: What happens if you push the toy?
• A1: It rolls away.
• Q2: What energy is stored within the toy? 
• A2: Potential energy.
• Q3: What is the energy when the toy was pushed
• A3: Kinetic Energy.
• Q4: What kind of energy is transferred to the toy?
• A4: Potential to Kinetic energy.

Work, Power and Energy
 So far, only the relation of work and energy is discussed. Work is a transfer of energy. Energy is the ability to do work while work is a transfer of energy. When work is done on an object, it gains energy. When work is done on an object, it loses energy.

Power is the rate of energy usage. In equation:

P = work/time = Energy/ time

The unit for power is joules per second. But if you are more familiar with watts which is named from a Scottish inventor James Watt who improved the steam engine technology. The conversion of joules per second to Watts is:

1 Watt = 1 joule/1 second

Activity 3: How Power-"full" am I?

Objective: After performing this activity, you should be able to compute for your power output.

Materials Needed:

• Stopwatch
• Meter-stick 
• Stairs

Procedure:

1. Enter your:
1. Name
2. Weight
2. Measure the stairs that you will climb.
3. Record the time it took just to walk up the stairs.
4. Solve the energy expended.
5. Compute the power output.

Name	Weight	Stair Height	Time Taken	Energy Expanded	Power
Alexander	54	5.0 meters	9.0 seconds	2025	145 J

Next Topic...

• Heat and Temperature
• Electricity
• Sound
• Light

Module 2

• Earth and Space

 






































































































































































































































































































Force, Motion, and Energy 

1. Laws of Motion 
 (4/26/2015) 
  
   1.1 Law of Inertia (p.3-12)
video: https://prezi.com/twmsbedasq8b/newtons-laws-of-motion-grade-8/

 Force- Objects can be moved by either pushing or pulling, this is referred to as force.

A. Balanced and Unbalanced force

• Balanced Force- Force acting equally on Magnitude and Line of action.

• Unbalanced Force: Forces acting unequally on Magnitude and Line of Action.

• Combined Force: Balanced + Unbalanced forces = Frictional force

• Combined Force: Gravitational Force + Tension = Magnitude

  - to accurately measure the force acting on an object is needed to be familiar with.

• Magnitude: Referred to size and strength of an object.

• Direction: Relative Magnitude of the force.

• Line of Action: Doubled force parallel to the force direction.

• Point of Application: Applied Force. 

B. Force Diagram:

• Gravitational Force-Object-Tension

C. Inertia and Acceleration

• Inertia: An object will remain at rest or move at constant velocity unless acted by an external net or unbalanced force.

• Acceleration: Acceleration of an object is directly proportional to to the magnitude of the net force and inversely proportional to mass.

• Net Force/Mass= Magnitude

• 
  

05.05.15

1.Law of Motion- Sir Isaac Newton actually has three laws of motion. They describe the relationship between a body and the forces acting upon it, and its motion in response to presumed forces.

First Law[Law of Inertia]: An object will remain its constant velocity unless acted upon by an external net or unbalanced force. 

•  Force: In physics, the push or pull of an object is referred to as force.

 Examole:

  A ball on top of a table is pushed and moves across a table and moves across the surface,got pushed to move faster,pushed to move in another direction of an object,or pushed in the opposite direction to make it stop.

Conclusion: Force can move,accelerate,change direction or stop an object.

• Balanced and unbalanced force:

 Can be accurately expressed by the properties of:

• Magnitude(or Newton): The size and strength of an object.

• Direction: Indicates where the force is heading and length represents relative magnitude.

• Line of action: An imaginary line that passes through the point of application.   

Activity 1: Forces on object at rest

Gravitational Force:

Example I: A pen hanging on a string is at rest but Gravitational Force will act on the pen causing it to fall.

Gravitational force <- pen
 
In this example, the pen is being acted by gravitational forces causing the pen to be attracted to the gravitational pull of the force.

Example II: A book is pushed across the table with a moderate amount of force will not move while another force with the same amount is pushing it in the opposite direction.

Moderate Force -> Object <- Moderate Force 


In this example, forces of the same mass at opposite directions pushing against an object will result no movement of the object.

Example III: A cardboard is being pulled away by a string with a moderate amount of force will move, but if another string is pulling it away with the same amount of force it will not move because of tension forces on either side.

Moderate Tension Force <- Object -> Moderate Tension Force 



In this example, forces of the same mass at opposite directions pulling against an object will result no movement of the object.

 


Quipper test - https://learn3.quipperschool.com/class/54ebebcc6d62353b1a007c1c/topic/537b7ed4b0237800020046c7/quiz/attempt/14/results


May 12, 2015

Activity 2: Balance of forces

There are two kinds of forces acting on an object that will result other forces to act. These are balanced and unbalanced force.

  -If you cut a string connected to a pen, the pen will fall. Or if you push a book one side across the table will not continue moving unless if you continue pushing it. The pen falls because there is no more force to counteract the force of gravity. The book moves because you are applying force to it. In other words, forces are no longer balanced. If an object is initially under at rest in an unbalanced force, it will go to the direction of the unbalanced force. But how will unbalanced force affect motion?

Example:

Place a ball on the desk and gently push it to one side. Observe
the motion as rolls down the desk. Eventually ball will stop because of frictional force. Again due to the unbalanced force, the object will change its velocity.  

Rewrite:


https://docs.google.com/document/d/114tAOGCbIhbkr6Zi39wwPvUSrppFGARMJTVdSNZhPyE/pub

05.19.15

Combining Forces:
 When we combine or add forces to determine the net or unbalanced force,we will limit our discussion to those forces which  act along the same line of action. The signs + and - are used to indicate the direction of the forces. Unlike signs are used for forces acting in the opposite direction,like in the case in of the book lying on the table. The gravitational force[Fg] and normal force [Fn] are assigned opposite signs -Fn is given a positive(+) sign is given a negative sign. If both Fn and Fg are given a magnitude value of three[3] units. The line will be:

Fnet = Fg + Fn
     = 3 units + (-3)units
     = 0

- If the expressions equate to zero, they are considered as balanced. And considered unbalanced if the expressions do not equate to zero. Unbalanced force change a body's state of motion.

Concept check:

• If two external nets are pulling a cube at the same time and direction with 10 units of magnitude each. The cube will move to the direction of the force.

• Example:

• Object -> External nets[10 units]

• This example explains that an objects moves to the direction where the external net is pulling it. 

• If two external nets are pulling a cube at the same time with opposite direction with 10 units of magnitude on one side and 5 units on the other. The cube will move to the direction with more force.

• Example:

• External net <-Object -> External nets[10 units]

• This example explains that an objects moves to the direction where the external net is pulling it.

• If three external nets are pulling a cube at the same time with opposite direction with two nets 5 units of magnitude in one direction  and 10 units on the other, the object will not move.

• Example:

• Object -> External nets[10 units]

• This example explains that objects wouldn't move if two equivalent units pulls one object in opposite directions.

https://docs.google.com/document/d/1ryYrmXoAtFlf4F4sA9uRLk2NUcPZfOA4IJuzlwRN2xw/pub


 May 26, 2015

watch these videos on inertia 
https://www.youtube.com/watch?v=6Qvb4XSNICA
https://www.youtube.com/watch?v=CQYELiTtUs8


and on force and acceleration
https://www.youtube.com/watch?v=JJrrhJ6b9lI
https://www.youtube.com/watch?v=ou9YMWlJgkE
https://www.youtube.com/watch?v=3FQ58lVtbCg


(Perform Activities 3 Investigating Inertia & 4 Force and Acceleration. These are in pages 10-17



Investigating Inertia: This activity is to demonstrate Newton's First Law of Motion.

Materials: 

• Empty Glass

• Card Board

• Coin

• Ruler     

Procedure: Coin Drop

1. First place the cardboard on the glass cup.

1. Then place the coin on the cardboard.

1. Slowly pull the cardboard away from the cup and observe what happens.

1. Put the card board with the coin back to the glass

1. Pull away the cardboard quickly away from the cup and observe what happens.

Explanation:

• If you cardboard slowly pull away from the cup, the coin will not drop since the coin is being carried by the unbalanced force of the cardboard.

• If you cardboard quickly pull away from the cup, the coin will not be carried by the cardboard and will remain at rest, because of the velocity of the cardboard being pulled, the coin would instead fall into the cup because of gravity.

II. Measure of Inertia: 
 All objects have the tendency  to resist changes in their state of motion or keep moving. However, changing the body's state of motion depends on inertia. A more massive object which has more inertia is difficult to move from rest, slow down, speed up or change its direction.

Newton's first law of motion states that  An object will remain at rest or move at constant velocity unless acted by an external net or unbalanced force.