Name Energy Storage and Transfer Model: Review Sheet Date Pd 1. A softball (m = 180 g) traveling at 22.3 m/s moves a fielder's glove backward 25 cm when the ball is caught. a. Construct an energy bar graph of the situation, with the ball and Earth s gravitational field as the system. b. How large is the average force exerted by the ball on the glove? 2. A bullet with a mass of ten grams is fired from a rifle with a barrel that is 85 cm long. a. Do an energy bar graph analysis of the situation. b. If the bullet leaves the barrel at 313 m/s, what force was used to fire the bullet? 3. A spring in a Nerf Rival gun is compressed. It can fire a 9 gram Nerf pellet at 30 m/s (~70 mph!). If the spring is compressed 10 cm, what is the spring constant of the spring inside the gun?
4. A 5.0 kg flowerpot falls from a window ledge 15.0m above the sidewalk. a. What is its potential energy at the top? b. What is the kinetic energy of the flowerpot as it reaches the sidewalk? c. With what speed does the pot strike the sidewalk? d. The flower pot is now moved higher up the building, to the 10 th floor, which is 30m above the sidewalk. Answer a-c for this new situation. e. At what height above the sidewalk must the flower pot be in order to double its speed hitting the ground? 5. How many times more kinetic energy does a car traveling 60 km/s have than a car traveling 30 km/s? Explain. 6. A car traveling down Middle Rd towards the round-about has 3000J of kinetic energy. The driver ignores the posted speed limit and decides to double their speed. How much kinetic energy will the car have? 7. Kinetic energy occurs due to an objects. How is it calculated? 8. The gravitational potential energy an object has is due to its. How is it calculated? 9. The spring potential energy a spring is storing is due to. How is it calculated?
10. Consider the 20 kg ball at each of the lettered positions as it moves down a frictionless track as it moves to position C. a. How much gravitational potential energy does the ball have at the start? b. How fast will the ball be moving at position A? at B? at C? c. If there was a spring at C with a spring constant of 250 N/m, how much would the spring compress if the ball came to a stop instead of continuing to move? 11. Three balls are rolled down three tracks starting from rest at the point marked start. start B A mid-height C mid-range finish Which one has the greatest speed at mid-range? Explain your reasoning. Which one has the greatest speed at the finish? Explain your reasoning.
. 12. A force of 800 N is needed to push a car weighing 25,000 N across a parking lot. If the car is moved 40 m, how much work is done? 13. How much work is done lifting a 60 kg crate up through a distance of 10 m? How much gravitational potential energy is now stored in the crate? How does the work done on the crate compare to the stored gravitational potential energy? 14. Find the height reached by the following objects: a. A rock (1.5 kg) thrown upward with a speed of 40 m/s- b. A pencil (0.05 kg) thrown upward with a speed of 45 m/s- c. A book (5 kg) thrown upward with a speed of 45 m/s- 15. A 100 kg shell is shot straight up from a cannon to the height of 50 m. a. What is the gravitational potential energy of the shell at the top? b. With what speed did the shell leave the cannon? 16. A 10 kg mass moves with a speed of 20 m/s. Find its kinetic energy. 17. A 12 kg rock falls from a cliff 25 m above a trail. a. What is its gravitational potential energy at the top? b. What is the kinetic energy as it reaches the trail? c. With what speed does the rock strike the trail? 18. Bart runs up a 2.91 m high flight of stairs at a constant speed in 2.15 seconds. If Bart s mass is 66 kg, determine the work which he did and his power rating.
19. On a recent adventure trip, Anita Break went rock-climbing. Anita was able to steadily lift her 80.0-kg body 20.0 meters in 100 seconds. Determine Anita 's power during this portion of the climb. 20. A physics teacher owns a family of squirrels. The squirrels have been trained to do push-ups in repetitive fashion. Being connected to an electrical generator, their ongoing exercise is used to help power the home. There are 23 squirrels in the family. Each squirrel has a mass of 1.1 kg. They do work on the up part of the push-up, raising their body an average distance of 5.0 cm. If the squirrels average 71 push-ups per minute, then determine the total amount of work done in one minute by the squirrel push-ups. How much power is generated by their activity? What? You don t like squirrels? 21. If the teacher doesn t move, will the pendulum bowling ball ever hit him? Explain why or why not? 22. Which book has less gravitational potential energy or are they the same? (Consider the reference point to be the floor.) If dropped, which will be moving faster? Assess the amount of kinetic energy each book will have if they are dropped off the desk. 23. When the rubber bands are stretched, where is the energy stored? How does the energy stored in each rubber band compare? 24. In the design of a roller coaster, is it possible for any hill of the ride to be higher than the first one? Why or why not?
25. A gymnast is swinging in a vertical circle around a bar. Explain, in terms of energy, why the gymnast s velocity is slowest at the top and fastest at the bottom of the circle? The following data were collected for two springs: 26. What are the spring constants of springs 1 and 2? 27. If there is a y-intercept, what does it mean? How will it affect your answer(s) to #28 and #29? 28. How much elastic potential energy would be stored if spring 1 and spring 2 were stretched from 0 to 0.40 meters? 29. How much energy would spring 1 and spring 2 store if they are now stretched from 0.40 to 0.80 m?
#30 and #31 are challenge conceptual questions. This level of problem will not be assessed on the exam. 30. Three identical blocks each take a different path from a height h to the ground. Block A is released from rest and falls vertically. Block B is released from rest and slides down a frictionless incline. Block C is projected horizontally with an initial speed v. a. Which block has had the greatest change in kinetic energy? b. Which block has the greatest kinetic energy just before it hits the ground? c. Which block has the greatest speed just before hitting the ground? 31. A toy car is released from rest at point A, and the elevation of the release point is indicated by a dot-dash line. The car rolls along the curved frictionless track as shown. The car will jump off of the track at point B and follow the dotted-line B projectile trajectory. After the car leaves the track and reaches the highest point in its trajectory, it will be at a different height than it was at point A. It doesn t make it back to its original height. Briefly explain why this is so. No friction, no air resistance.