Topic 1 Work

Define work, as the term is used in physics to express the transfer of energy 

Topic 2 Conservation of Energy

Given Newton's laws of motion, show why energy must be conserved in any interaction.

Topic 3 Forms of Mechanical Energy

List three forms of mechanical energy

Topic 4 Units

How is a joule of energy, as expressed in the modern SI units, related to ergs and ft-lbs?

Topic 5 Power

(a)   Define Power in terms of energy and time.

(b)  What are the units of power?

Topic 6 Machines

Topic 7 Collisions

Define the Coefficient of restitution.

Examples

A lame old man is leaning on his shopping cart while pushing it at constant velocity toward the produce section of the supermarket.

He pushes it 5.0 m across the supermarket with a force of 150 N directed 75^o below the horizontal. The fully loaded shopping cart weighs 200 N and it takes him 20 s to go that far.

Find: (a) How much force is needed to overcome friction? [39 N]

(b) How much work does the old man do? [195 J]

(c) What power does the old man exert in Watts? [9.75 W]

A 10kg cake of ice starting from rest slides down a chute that is 6.7 m long and inclined 30^o to the horizontal. The ice reaches the bottom of the chute with a speed of 7.6 m/s.

Find: (a) What is the potential energy of the cake of ice at the top of the chute?

(b) What is the kinetic energy of the ice at the bottom of the chute?

(c) At what rate is mechanical energy converted to heat?

Textbook Problems