Newton's Laws of Motion

Newton's Laws of Motion

Unit 4 Notes

Newton's First Law of Motion

(The Law of Inertia)

An object in motion stays in motion, or an object at rest stays at rest until an unbalanced net force acts upon it.

Inertia - the tendency of an object to resist any change in its motion.

Example of Newton's First Law of Motion and an example of why we have seatbelts

Newton's Second Law of Motion

A net force acting on an object causes an object to accelerate in the direction of the force.

Force (kg x m/s²) = mass (kg) x acceleration (m/s²)

Can be written as:

F=ma

a=F/m

m= F/a

Acceleration is determined by the size of force and the mass of an object.

An example of Newton's Second Law of Motion, implying that objects with greater mass need more force in order to accelerate.

Newton's Third Law of Motion

(The Law of Action-Reaction)

For every action (or force) there is an equal and opposite reaction (or force).

Momentum - property of a moving object resulting from its mass and velocity.

Momentum (p)= mass x velocity

An example of Newton's Third Law of Motion showing that for every action, there is an equal and opposite reaction

Practice Time

Let's see if you can distinguish between the three laws of motion

Multiple Choice

An object at rest will _____ if not outside forces are applied.

• Stay at rest
• Decrease mass
• Increase velocity

Multiple Choice

Forces always act in equal and opposite pairs.

• Newton's 1st Law
• Newton's 2nd Law
• Newton's 3rd Law
• Newton's 4th Law

Multiple Choice

If an object is stationary (not moving) the forces acting upon it are---

• Balanced
• Unbalanced
• Weak
• Hulk Smash?

Multiple Choice

45 meters per second squared is the--

• Acceleration
• Mass
• Weight
• Force

Multiple Choice

20 N is the ----

• Mass
• Force
• Acceleration
• Weight

Multiple Choice

1000 kg is the -----

• Force
• Mass
• Acceleration
• Weight

Multiple Choice

How many laws of motion does Newton have?

• One
• Two
• Three
• Four

Multiple Choice

Which has more inertia--

• Truck
• Cat
• Ant
• Skateboard

Multiple Choice

What Newton's law does this picture represent?

• Newton's 2nd law
• Newton's 1st law
• Newton's 3rd law
• Newton's 5th law

Multiple Choice

The law in the picture represents---

• Newton's 1st law
• Newton's 2nd law
• Newton's 3rd law
• Newton's 4th law

Multiple Choice

According to Newton's Second Law, if you increase the force applied to an object:

• It accelerates more
• It doesn't move
• You get more inertia
• It decelerates

Multiple Choice

What is Newton's Third Law of Motion?

• Object in motion stays in motion and an object at rest stays at rest unless acted on by an unbalanced force
• Force = m x a
• For every action there is an equal and opposite reaction

Multiple Choice

What is the standard unit force is measured in?

• Newton
• Gram
• Pound
• Meter

Multiple Choice

Which force produces a change in motion?

• Unbalanced force
• Balanced force
• Gravitational force
• Frictional force

Multiple Choice

What is Newton's Second Law of Motion?

• F = m x a
• Action/Reaction
• Object in motion will stay in motion, object at rest will stay at rest
• Velocity

Multiple Choice

A _______ is a push or pull.

• Newton
• Acceleration
• Momentum
• Force

Multiple Choice

Which law best describes a satellite orbiting the earth?

• Law of Inertia
• Law of Mass and Acceleration
• Law of Action Reaction

Multiple Choice

What pulls a ball back to earth?

• Gas
• Friction
• Gravity
• Molecules

Multiple Choice

What is Newton's First Law of Motion?

• F = m x a
• Every action has an equal an opposite reaction
• An object at rests stays, an object in motion stays in motion
• Friction

Multiple Choice

When a heavy football player and a light one run into each other, who exerts more force?

• The heavy one
• The light one
• They are equal
• There is no such thing as force