Chapter 12 Work and Energy

1
Chapter 12Work and Energy

• Section 1
• Work, Power, and Machines
• p. 378

2
Objectives

• Understand simple machines
• Evaluate the relationship between energy, work,
  and power

3
I. Work- transfer of energy to a body by the
application of a force that causes the body to
move in the direction of the force
A. WF x d for work to take place
there must be movement B. Measured in Joules
1 J 1 N x m 1 kg x m2/s2
II. Power the rate at which work is done or
energy transformed A. Power work/time P
w/t B. Measured in watts WJ/s
4
III. Machines and Mechanical Advantage
A. Machines multiply and redirect force
B. Mechanical Advantage- how much a
machine multiplies force or increases
distance 1. Ratio between output force and
input force 2. Ratio between
input distance and output distance (if friction
is ignored- ideal mechanical advantage)
3. MA output force/input force input
distance/output distance
5
Homework

• Stairs worksheet
• Read 12.1 and 12.2