Problem Set 6: Work and Conservation of Energy
1. A cart starts at the top left of the roller coaster shown above. Ignoring air resistance and friction, the farthest position or region attainable by the cart is:
a. region A b. position B c. region C d. position D e. E or beyond
2. A young girl wishes to select one of the frictionless playground slides illustrated below to give her the greatest possible speed when she reaches the bottom of the slide.
Which of the slides illustrated in the diagram should she choose?
a. A b. B c. C d. D e. It doesn't matter, her speed would be the same for each.
3. A brick is lifted to a given height and then dropped to the ground. Next, a second identical brick is lifted half as high as the first and also dropped to the ground. When the second brick strikes the ground it has
a. half as much kinetic energy as the first
b. as much kinetic energy as the first
c. twice as much kinetic energy as the first
d. four times as much kinetic energy as the first
e. impossible to tell
4. A brick is lifted to a given height and then dropped to the ground. Next, a second brick, which weighs twice as much as the first, is lifted just as high as the first and then it too is dropped to the ground. When the second brick strikes the ground, it has
a. half as much kinetic energy as the first
b. as much kinetic energy as the first
c. twice as much kinetic energy as the first
d. four times as much kinetic energy as the first
e. impossible to tell
5. If you lift one bag of groceries up five flights of stairs, how much work do you do compared to lifting the same load up only one flight of stairs?
a. five times as much b. Twice as much. c. The same amount d. One fifth as much.
6. As a pendulum swings back and forth,
a. potential energy is transformed into kinetic energy.
b. its energy is all kinetic at the lowest part of its swing.
c. its energy is all potential at hte end points of swing.
d. All of the above.
7. A 1200-kg out of control car enters an escape surface made of loose gravel inclined upward at 5°. The force of friction is 1200-N. Determine the initial speed of the car when it entered the escape surface.
8. A 500-kg roller coaster ride has a braking system using a spring of force constant of 21500 N/m. If the rollercoaster has a speed of 23 m/s when it first touches the spring, how far does the spring compress by the time the car stops?
9. A 500-kg car initially moving at 20 m/s coasts down a hill for 2000 m before stopping. If the friction force is 800 n, what is the angle of the incline?
10. If you drop a 50-kg object from 10-m height, how fast is it going by the time it reaches the ground? Solve this using LCE, and using kinematics.
823 Conservation of Energy Practice Set 6