ForceMotion

Energy

For an object to move, there must be an application of force.

Force is a push or a pull that causes an object to move, change direction, change speed, or stop.

Push

Pull

Newton’s First Law of Motion

An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by a force.

Applying force can cause motion, a change in the position of the object.

Force

Applied force caused a change in position of the car!

Energy is required to apply force.

Energy is the ability to do work by applying force.

Force was applied to lift the rocket into the air!

Let’s see what happens to the

potential and kinetic energy of the biker as

he goes up the hill!

Two kinds of Energy

Potential Energy - Stored energy

Kinetic Energy - The energy of motion

Force

As the biker goes up the hill, kinetic energy decreases while potential energy increases.

Force

At the top of the hill, the biker has maximum potential energy but minimum kinetic energy.

As the biker goes down the hill, kinetic energy

increases while potential energy decreases.

At this point, the biker has stored energy that

can be used to go down the hill.

Potential Energy

If an object is not in motion, it has potential energy. Potential energy is a result of stored energy or energy due to position.

Drawn bow has stored energy.

Water at the top of a waterfall has stored energy.

Ball about to be dropped has stored energy.

Compressed spring has stored energy.

Potential energy depends on mass and height of the object.

Lower height:

Lower potential energy

→ Lower impact

Higher height:

Higher potential energy

→ Higher impact

Larger weight:

Higher potential energy

→ Rolls down and reaches bottom faster

Lower weight:

Lower potential energy

→ Rolls down and reaches bottom slower

Potential Energy converted to Kinetic Energy…

When stored energy begins to move, the object transfers energy from potential energy into kinetic energy.

Standing Running

Kinetic Energy

If an object has motion, it has kinetic energy.

Vibration of the telephone causes motion.

Car going down the road has motion.

Spinning a ball has motion.

Jumping rope results in motion. They all

have kinetic energy!

Kinetic energy depends on mass and speed of the object.

Lighter Load:

Lower kinetic energy → Easier to push/pull

Heavier Load:

Higher kinetic energy → Harder to push/pull

Slower Speed:

Lower kinetic energy → Slower acceleration

Higher Speed:

Higher kinetic energy → Faster acceleration

Measuring Energy

• Just like time, distance, and speed, energy can be measured.

• Energy is measured in joules (J).

• How much is 1 J? One joule is equal to the energy required to lift a small apple (100g) vertically one meter.

• Potential and kinetic energy

are both measure in joules.

Example in…

What happens to the kinetic and potential energy of the bird as it is released?

While the bird is ascending, kinetic energy is decreasing and potential energy is increasing.

The bird is at the top of the trajectory. At this point, kinetic energy is at a minimum while potential energy is at a maximum.What happens to the kinetic

and potential energy of the bird as it falls back to the ground?

While the bird is descending from the top, the kinetic energy is increasing and potential energy is decreasing.

Let’s test our understanding of

potential and kinetic energy!

Good job!

Which skater has the highest kinetic energy?

The yellow shirt skater has the highest kinetic

energy.

Which skater has the lowest

kinetic energy?

The blue shirt skater has the lowest kinetic

energy.

Which skater is transferring energy

from potential energy to kinetic

energy?

The red shirt skater is transferring from potential energy to

kinetic energy.Which skater

has the lowest potential energy?

The yellow shirt skater has the

lowest potential energy.Which skater

has the highest potential energy?

The blue shirt skater has the

highest potential energy.

What is the order of sequence for

increase in potential energy?

The correct sequence is

yellow, red, blue.What is the order of

sequence for increase in kinetic

energy?

The correct sequence is blue,

red, yellow.

Summary• Potential and kinetic energy are two types of energy.• Potential energy is stored energy.• Kinetic energy is energy of motion.• Both depend on mass of the object. Potential energy

also depends on position of the object, while kinetic energy also depends on the speed of the object.

• Potential energy can be converted to

kinetic energy, and vice versa.• Potential and kinetic energy are measured

in joules.

Fin!