Lesson: Newton, Force, and Acceleration

Newton: Force Inertia Acceleration

By William Lovering

Multiple Choice

What is the unit to MEASURE force?

• Kilogram
• Meter
• Pascal
• Newton

What is net force?

• Forces could be balanced or unbalanced

• There can be multiple forces acting on an object

• Forces in opposite directions cancel each other. Forces in the same direction help each other.

• Net force is the force an object experiences or "feels" after you sum (add or subtract) all of the forces.

  • Add if in the same direction​.

  • Subtract if in opposite directions

Multiple Choice

Forces that have a net force of zero

• Balanced force

• Unbalanced force

Multiple Choice

A(n) _______ is present if velocity changes.

• unbalanced force

• balanced force

• machine

• gravitational force

Multiple Select

Which of the following would NOT require an unbalanced force? (Choose all that apply)

• an object remains at rest

• an object moving in a straight line at a constant speed

• an object moving in a circle at a constant speed

• an object slowing down in a straight line

Multiple Choice

What is the net force?

• 17N Left

• 3 N, right

• 10N Right

• 3N Left

Multiple Choice

If an object is not moving the forces acting upon it are _____________

• unbalanced
• weak
• balanced
• Hulk Smash!

Newton's First Law

• An object in motion tends to stay in motion unless acted upon by an unbalanced force.

• An object at rest tends to stay at rest unless acted upon my an unbalanced force.

• The first law is often called the law of inertia.

• Inertia means that an object usually resist a change in motion. The more mass an object has, the more inertia it has. For example, a train has more inertia than feather.

Forces can be balanced or unbalanced

When a force is balanced, it will move with a constant velocity (staying still or moving at the same speed)

When a force is unbalanced, it will accelerate in the direction of the larger force.

Net force is the combination of all the forces acting on an object. If the forces are going in the same direction they can be added on top of each other.

Multiple Choice

The rate at which velocity changes is called 

• motion
• average speed
• instantaneous speed
• acceleration

Multiple Choice

Acceleration of an object happens when things ________

• slow down
• go faster
• change direction (turn)
• All of the above

Multiple Choice

A force which is present in all objects with mass.

• gravity

• friction

• normal

• inertia

Multiple Choice

The force that opposes gravity when an object doesn't fall.

• gravity

• magnetism

• normal

• friction

Multiple Choice

A force that opposes motion when matter touches

• gravity

• magnetism

• normal

• friction

Newton's Second Law

• F= m * a

• m=F/a

• a = F/m

• The more mass an object has, the more force is needed to accelerate it. The more force you apply, the more it will accelerate. There are a lot of applications of Newton's Second Law.

Multiple Choice

What is the acceleration of an object that has a mass of 5 g and is hit with a force of 10 N?

• 50 m/s²

• 2 m/s²

• 15 m/s²

• 5 m/s²

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

If the man pushes with an equal amount of force, which object will accelerate more?

• Car because it has more mass

• Lawnmower because it has less mass

• Car because it has less mass

• Lawnmower because it has more mass

Multiple Choice

An object with a mass of 100 kg is observed to accelerate at the rate of 5 m/s². Calculate the force required to produce this acceleration.

• 20N

• 500 M/S

• 20 Kg

• 500N

Multiple Select

Which statement, or statements about the relationship between mass, force, and acceleration is true? (you may select more than one answer)

• An object will accelerate (change velocity) if a force is applied.

• If the same force is applied to 2 objects with different mass, the one with more mass will accelerate less.

• If forces of different strength are used on 2 objects with the same mass, they will still accelerate (change velocity) at the same rate.

• If you reduce the mass of an object, you can have the same acceleration with less force.

Multiple Choice

While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?

• Firefly

• Bus

• Equal Forces

Multiple Choice

What is Newton's Third Law of Motion?

• an object at rest stays at rest, and an object in motion will stay in motion until an outside force acts upon it

• the acceleration of an object will be equal to the net force of an object divided by its mass

• for every action, there will be an equal and opposite reaction

• an object that is not moving will stay not moving moving until an unbalanced force acts on it

Multiple Choice

If you throw a ball into the air, Earth exerts a force on the ball. The ball in the air exerts no force on Earth.

• True; all forces act alone

• False; there will always be a force pair

Multiple Choice

When you jump up, you push the earth downwards. Why can't you tell that the earth has moved?

• The force of you jumping up doesn't actually push the earth down.

• The earth has much more mass so it doesn't move at all

• The earth is firmly rooted

• The earth has much more mass so you can't tell that it moved

Multiple Choice

When you hit a tennis ball with a racket...

• The ball exerts more force on the racket

• The ball and racket exert the same force on each other

• The racket exerts more force on the ball

• It depends on how hard you hit it

Multiple Choice

When you jump upwards, what force is moving you upwards once you leave the ground?

• Gravity on to you

• The air on to you

• You on to the earth

• There is no upward force once you leave the ground

Multiple Choice

A player hits a ball with a bat. The action force is the impact of the bat against the ball. The reaction force is...

• The grip of the player's hands on the ball
• the air resistance of the ball
• the force of the ball against the bat

Newton's Laws Summary

Newton's 1st Law: The Law of Inertia

Objects resist changing their velocity. This resistance is called inertia. Whatever velocity an object has, it will keep that velocity until an unbalanced force causes it to change. ​

 I can explain the relationship between forces and motion and use that to predict changes in motion using Newton's Laws.

Newton's 2nd Law: F, M, and A​

There is a mathematical relationship between force, mass, and acceleration. The amount of force on an object equals the amount of mass times the amount of acceleration (F = ma). More mass = more inertia. Inertia works against force. (Force wants to change velocity, inertia wants it to stay the same). How fast an object accelerates depends on the amount of force used and the mass of the object.

​

Newton's Laws Summary

Newton's 3rd Law: Action and Reaction Forces.

When a force is applied to an object, the object always applies a force back that is equal in strength and in the opposite direction. The first force is called the "action force" and the second is called the "reaction force". Together they make a "force pair".

Some text here about the topic of discussion

Multiple Choice

Which of the following is the cause of an acceleration?

• speed

• inertia

• force

• velocity

Multiple Choice

A player throws a ball. The action force is the player pushing on the ball. The reaction force is...

• The force of the ball pushing on the player

• The force of the grip of the ball
• The celebration the player is thinking of

Multiple Choice

What is the reaction force to a foot pushing down on the floor?

• The foot going through the floor
• The floor pushing back against the foot
• The floor breaking to the foot

Multiple Choice

If a net force is acting on an object, 

• its velocity must be constant
• its velocity must be changing
• its mass must be changing
• its acceleration = 0 

Multiple Choice

The tendency of an object to resist a change in its state of motion is called the object's ______.

• incline
• straight line
• friction 
• inertia 

Multiple Choice

Without a force to stop or slow a coasting object, what will happen?

• it will coast in a straight line forever

• It will keep the same speed but eventually change direction

• It will slow down with time

• It will explode

Multiple Choice

A change in velocity over time is called ___________.

• speed
• force
• acceleration
• direction

Multiple Choice

The increasing speed of a falling object is caused by _____________.

• force
• mass
• speed
• gravity

Multiple Choice

Which law explains why the driver "keeps moving forwards, even though the car has stopped"?

• 1st

• 2nd

• 3rd