Section 3

What Is Energy?

But first, let’s review:

1. How do we define work?

Energy transferred by a _____ Force applied to a body Body moves in _______________

force

direction of force

2. How do we calculate work?

Work = ______x _________distanceforce

Unit for work ________.Joule (J)

But first, let’s review:

1. How do we define Power?

The rate at which _____ is done. work

2. How do we calculate power?

Power = timework

Unit for power_________.Watts (W)

I. Energy & Work

A. Energy – ability to do work.REMEMBER: work is applying a force to something in order to move it.

dd

work = force x distance

1. Energy – No change in position required. (no movement)

Both the wrecking ball & the bow possess STORED energy.

B. Energy must have the ability and/or cause a change in position.

1. In other words: energy can be transferred.

II. Potential EnergyA. Potential Energy – Stored Energy, sometimes

referred to as positional energy

Elastic Potential Energy

B. Gravitational Potential Energy – Depends on the mass & height of an object.

III. Kinetic EnergyA. Kinetic Energy – Energy of a moving

object.

Kinetic Energy = ½mass x velocity2

KE = ½mv2

Kinetic EnergyPotential Energy

GPE = mass x acceleration x height

Mass = kilogram (kg)

Acceleration = 9.8m/s2

Height = meters

KE = ½mass x velocity2

Mass = kilogram (kg)

Velocity = m/s

Pg. 395, questions 1 – 3 Pg. 393, questions 1 – 4