PHYSICS 3200: Heat Light and Sound

Start Reading the chapter on Heat and Temperature by Monday, March 17.

Assignment 3: Due Monday, March 17.

1. A block that weighs 100N is moving rapidly along a level surface. I push on it with a force of 50N opposite to the direction it is moving. How much work do I do as the block travels 3m?

2. A 1,500kg car is moving with a speed of 20m/s. What is its kinetic energy? How much work will have to be done on the car to stop it?

3. If I can exert a braking force of magnitude 12,000N on the car in the previous question, how far will the car travel before it stops?

4. A 3kg block is 7m above the ground and a 5kg block is 4m above the ground. Which block has the most gravitational potential energy relative to the ground? (I want to see your calculation.)

5. I am holding a 0.3 kg ball motionless at the top of a cliff, 60m above the ground. What is the potential energy of the ball? What is its total energy, i.e. kinetic plus potential?

6. The ball in the problem above is dropped, i.e. from 60m above the ground. If air resistance is negligible, what is its total energy, i.e. K.E. + P.E., when it is 50m above the ground? What is its kinetic energy then?

7. When the ball above reaches the bottom, i.e. just before it hits the ground, what will its kinetic energy be? What is its potential energy?

8. If I have a light bulb that has an efficiency of 6%. How much electrical energy will be required to produce 150J of light?

9. Could I have a machine where I put in 1200J of energy and get 1500J of useful work out? (Give a reason for your answer.)

10. A person is doing work at a rate of 500W. How much work will she do in one hour?

We will have a quiz over motion and forces on Monday, March 10.

I will provide the formulas below on the exam.

Change in Position = Final position – Initial position		1N = 1kgm/s^2
		F = Ma
Weight = Mg	g = 10m/s^2