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 = time work 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. d d 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 Energy A.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 Energy A.Kinetic Energy –Energy of a moving object. Kinetic Energy =½mass x velocity 2 KE = ½mv 2

Kinetic EnergyPotential Energy GPE = mass x acceleration x height Mass = kilogram (kg) Acceleration = 9.8m/s 2 Height = meters KE = ½mass x velocity 2 Mass = kilogram (kg) Velocity = m/s Pg. 395, questions 1 – 3 Pg. 393, questions 1 – 4