8.2 EFFECT OF FORCE

8.2 EFFECT OF FORCE

by KASMAWATI Moe

​Learning objectives

​1.Identify how forces affect motion

2.Identify how the resultant force changes the motion of an object

3.Differentiate between mass and weight

4.Define the relationship between force, mass and acceleration

5.Define motion in circular path

6.Identify the effect of air resistance to the motion of free falling object

7.Express the momentum and impulse of the force

8.Calculate the resultant force

​Forces and motion

​Whenever we push or pull an object a force acts upon them and makes them move from one place to another.

​​Forces and motion

​​Hence, force can –

1. initiate motion in a motionless object

2. change (increase or decrease) the velocity of the moving object

3. alter the direction of a moving object

4 change the shape and size of an object

​Force Quantities

​1. Forces are vector quantities because they have both size and direction.

​2. Forces are measured in newtons (N)

​3. Small forces can be measured using a spring balance (or newton meter)

​Newton as a founder of Law of motion

​FORCE, MASS AND ACCELERATION

​3rd Law of Motion

​Balanced and unbalanced force

​Balanced forces:

If the forces acting on an object are balanced then the object will either remain stationary or continue to move with a constant speed

​

​Unbalanced forces:

If the forces acting on an object are unbalanced then the object will change its speed.  It will begin to move, speed up, slow down or stop.

Multiple Choice

At the start of a football game, a footballer kicks a ball placed in the middle of the field to move the ball.

What is the effect of force on the object?

• Change the direction of a moving object

• Make a moving object stop

• Make a moving object move slower

• Make a stationary object move

Multiple Choice

What is mass?

• The amount of liquid something has

• how much something weighs

• The amount of matter in an object

• The amount the object weighs on earth

Multiple Choice

Frank pushed two balls with different masses with the same force, how did the motion of the ball with the greater mass differ from the ball with less mass?

• The ball with a greater mass moved a shorter distance

• The ball with the greater mass will move in a different direction

• The ball with the greater mass moved for a longer time

• The ball with the greater mass will move with more speed

Multiple Choice

When on a skateboard and pushed down the ramp, what would increase your speed going down a skate ramp?

• decrease the angle

• decrease the force

• increase friction

• increase the force

Multiple Choice

After hitting a golfball, what does Friction cause a golf ball to do?

• to bounce

• increase speed

• decrease speed

• beat gravity

Multiple Choice

What forces are acting on the bag, and what are their relative magnitudes and directions?

• The force of gravity on the bag and the force of the hook. The force of gravity is larger than the force of the hook. The force of gravity points downward and the force of the hook points upward.

• The force of gravity and the force of the bag. The force of gravity is exactly balanced by the force of the bag. The force of gravity points downward and the force from the bag points upward.

Multiple Choice

For every action there is an equal and opposite reaction

• Newtons 1st Law

• Newtons 2nd Law

• Newtons 3rd Law

• None

Multiple Choice

Force= mass x Acceleration

• Newtons 1st law

• Newtons 2nd law

• Newtons 3rd law

• None

Multiple Choice

A force of 90N is applied to each cart below, which one will accelerate the fastest?

• Cart 1
• Cart 2
• Cart 3 
• Cart 4

Multiple Choice

What is Newton's 2nd Law?

• F=ma

• Every action has an equal and opposite reaction

• An object at rest stays at rest, an object in motion stays in motion.

• Friction

Multiple Choice

If these teams are pulling with the same amount of force what will happen?

• The boy in blue will win.
• They will not move at all.
• The boy in red will win.
• Both will fall down.

Multiple Choice

What are Newton's 3 Laws? 

• Law of Action-Reaction, Law of Inertia and Law of Velocity
• Law of Speed, Law of Action-Reaction, Law of Force and Acceleration
• Law of Inertia, Law of Force and Acceleration, and Law of Action-Reaction
• Law of Mass and Acceleration, Law of Action-Reaction, and Law of Inertia

Multiple Choice

Newton's second law states that greater the mass the more _________ will be needed to move the object.

• power

• force

• distance

• speed

Multiple Choice

In a football game, the goalkeeper stops a moving ball to prevent it from entering the goal.
What is the motion of the object?

• Change the direction of a moving object
• Make a moving object stop
• Make a moving object move slower 
• Make a stationary object move

Multiple Choice

In a football game, the footballers kick the rolling ball to make it move even faster.
What is the motion of the object?

• Change the direction of a moving object
• Make a moving object stop
• Make a moving object move faster
• Make a stationary object move

Multiple Choice

which of the following is not an effect of force:

• to move a body from rest

• to stop a moving body

• to change the colour of an object

• to change the shape of a body

Multiple Choice

in the given figure force is

• changing the direction of motion

• changing the shape

• stopping a moving object

• none of the above

Multiple Choice

Which of the following images shows a pull?

Multiple Choice

What effect will the force done by the red player?

• The ball will stop moving.

• The ball will permenantly change shape.

• The ball will slow down.

• The ball will change the direction of its movement

Multiple Choice

A force can____________.

• make an object move

• make a moving object stop moving

• slow an object down

• all of the above

Multiple Choice

True or false: An object resting on the ground can move without force.

• True

• False

Multiple Select

A force can make a moving body move faster

• true

• false

Multiple Choice

The upward force exerted by a liquid on an object immersed in or floating on the liquid

• pressure
• buoyant force
• normal force
• gravity

Multiple Choice

When the weight of an object is greater than the buoyant force, the object will ... 

• Sink
• Float 
• Expand
• Shrink

Multiple Choice

What direction is the buoyant force in?

• Downward
• Left
• Right
• Upward