Assignment 2
Work and Energy
Read chapter 8 from Hewitt (pages 103 to 118) Good advice: use the review questions 1 - 20 on pages 119 to 120 as a "reading guide".
The very basic:
Question 1. How much gravitational potential energy is possessed by a 25 kg mass held at a height of 12 meters? The acceleration of gravity is -9.81 m/s/s by most references. You should generally round this value to -10 m/s/s.
Question 2. How much kinetic energy is possessed by a 12 kg mass traveling at 5 m/s?
Question 3. A spring is stretched by 2.5 meters from its "relaxed" length by a force of 5.0 N.
3a. What is the spring constant (k) for this spring?
3b. How much energy is stored in the spring when it given an elongation (∆x) of 2.0 meters?
Question 4. How much work is required to slide a refrigerator across a floor at constant speed if a 400 N force is required and the movement occurs over 4.0 m?
A little less basic:
Question 5. A pendulum is found to have a mass of 2.0 kg and its bottom edge is located 1.4 m above the ground at its highest point. How fast is it moving at its lowest point if it just barely misses touching the ground on its swing?
Question 6. A ball is dropped from a height of 12.0 meters. How fast is it traveling when it passes the 6.0 meter mark on its way down?
Look at the physlet located at: http://www.physicsclub.net/physlets/physletprob/ch8_problems/ch8_3_work_energy/New_work_energy8_3_1.html
It may be easier to navigate from this sequence of links: physicsclub home page | Energy Basics | Ball in a Bowl
Question 7: How fast is the green ball moving at the bottom of the bowl?
Hint: Use the top of the green ball as a reference when you get the coordinates and remember that ∆Ep = ∆Ek
Look at the physlet located at: http://www.physicsclub.net/physlets/physletprob/ch8_problems/ch8_3_work_energy/work_energy_1.html (or navigate: home page, energy basics | work on a bowling ball)
Question 8: After trying all four animations, rank the four paths from most work by gravity to least work by gravity.