1. Two puppies are fighting over a toy. Each puppy grips one end of that toy in its mouth and pulls. Suddenly, the puppy on the right pulls especially hard on the toy and moves its end of the toy to the right. The other puppy manages to keep its end of the toy from moving. Alas, the toy breaks and the game ends. Breaking the toy required energy and that energy was provided
2. You make a sharp left turn in your car and your cellphone slips off the dashboard and out the right passenger window. The cellphone leaves the car because
3. You are pulling your niece uphill on a sled and the sled experiences a small downhill frictional force as it slides uphill on the snow. Your niece is traveling in a straight line at a constant speed. The net force your niece is experiencing is
4. You are rearranging your room and are now sliding your desk across the floor at constant velocity. Which of the following statements about the forces acting on the desk is correct? [Consider only horizontal forces]
5. In the game of shuffleboard, you push plastic disks forward and then release them so that they slide across a level playing surface. Once you release a disk, you are no longer pushing and it gradually skids to a stop. Its final position determines your score. As each disk skids to a stop, what becomes of the kinetic energy it had when you released it? That energy is
6. You are carrying a child on your back as you walk down a hill. The child is traveling straight at a steady speed. In which direction is the force you are exerting on the child?
7. You take off your shoes to sneak quietly into your home late at night. Unfortunately, it’s too dark to see the concrete block your friend left on the floor and your big toe collides with it. The block doesn’t move and your foot comes to a complete stop due to the impact. Luckily, you are wearing soft woolen socks because when your foot stops during the impact, your toe transfers
8. A rigid two-blade wind turbine that is experiencing zero net torque
9. A dog and a cat jump horizontally off a wall at the same moment and soon land on the level horizontal field that extends outward from the base of the wall. The dog weighs twice as much as the cat, but the cat was moving forward horizontally twice as fast as the dog when the two animals left the wall. In this situation,
10. A skateboarder rides swiftly up the edge of a bowl-shaped surface and leaps into the air. While in the air, the skateboarder flips upside and tosses the skateboard from hand to hand. The skateboarder then rides safely back down the bowl. During the time that the skateboarder and skateboard are not touching anything, one aspect of their motion that is constant is their total (or combined) [note: neglect any effects due to the air]
11. You are tossing popcorn straight up and catching it in your mouth. At the moment each piece of popcorn reaches its peak height, its velocity is
12. Running on soft dry sand is exhausting, so you switch to running on hard wet sand. The hard wet sand removes less energy from you because
13. You’re at the lake and watch two children jump off a dock. They jump at the same time and at the same speed, but the boy jumps mostly upward while the girl jumps mostly forward. After they leave the dock,
14. It is a beautiful summer day and the residents of a high-rise apartment building are eating dinner on their balconies. A resident accidently knocks an empty glass off a balcony that is about 80 meters (260 feet) above the cement patio. The glass would have smashed on that patio after falling for 4 seconds, however, a quick-witted resident catches the glass after it has fallen for only 2 seconds. How far above the patio was the glass when it was caught?
15. You are at the gym, exercising on a step machine. You have one foot on each of the machine’s pedals and you move those pedals up and down as you step. The pedals always push upward on your feet, but they push upward harder on your feet while moving downward than they do while moving upward. When during this exercise is your foot transferring energy to the pedal that it is touching?
16. A juggler tosses a club straight up. Disregarding any effects due to the air, what force or forces are acting on the club while it is above the juggler’s hands?
17. Two children are balanced on a seesaw, but one child weighs twice as much as the other child. The heavier child is sitting half as far from the pivot as is the lighter child. Since the seesaw is balanced, the heavier child is exerting on the seesaw
18. You are standing in the middle of a subway car that is moving forward at constant velocity when another passenger accidently spills an enormous container of olive oil. Suddenly, the floor cannot exert any frictional forces on your feet. Because nothing else is touching you, you
19. You are practicing tennis alone by hitting a tennis ball forward toward a cement wall. Each time the ball hits the wall, it bounces backward at high speed so that you can hit it again. During its bounce, the ball
20. Your table at a family-style restaurant has a “lazy Susan” in the middle. This large circular platform rotates frictionlessly so that you can “pass” an entree to your friends by placing it on the platform and then rotating the platform. When the server places a new entrée on the platform, it
21. A cross-country skier is struggling to get up a hill, so you offer to help. As the skier passes you, you reach out with your hand and exert an uphill force of 80 N (18 pounds) on the skier. When you do this, the skier exerts