You are trying to open a jar of honey and find that the lid is stuck. You are twisting the lid in the opening direction, but it won't budge. To succeed in opening the lid, what must you do?

You and your friends manage to get the Ruffner Bridge (the pedestrian bridge over Emmet Street) bouncing up and down vigorously. At what point(s) during its bounce is the bridge moving fastest?

You are graduating and you toss your cap into the air. While the cap is not touching anything and neglecting any effects due to the air, what aspect of the cap's motion remains constant?

A shelf breaks and your entire collection of stuffed animals begins to fall simultaneously from the same height. Neglecting any effects due to the air, which of the animals reaches the floor first?

Your friends have made a huge batch of lemonade and they need a huge ice cube to chill it. After buying the ice cube, they tie the cube in the middle of a pickup truck's horizontal bed and begin driving home. While the truck and its contents are all moving forward horizontally at constant velocity, the ropes break so is nothing holding the ultra-slippery ice cube in place. The ice cube

A water bottle is touching the top of a table. The downward force the water bottle exerts on the table

A weight-lifting competition leaves you so exhausted that you sleep right through to the 22nd century. When you awake, you learn that your next competition is on the moon, where gravity is much weaker than on Earth. Your trainer has brought your favorite 100-kilogram bar to the moon with you. That bar

Which of the following is experiencing zero net force?

You throw your water bottle straight up and it rises for 2 seconds before reaching its peak height of about 20 meters (66 feet). After only 1 second of rising, what was the water bottle's approximate height?

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

You are heading south for spring break and have boarded a plane at the local airport. The plane starts its engines and its propellers begin to spin. They spin slowly at first, then faster and faster over a period of many seconds. Why don't the propellers reach full rotational speed immediately?

Builders obtain a vertical reference line by hanging a small but heavy object on a string beneath a fixed support point. Why does that system (object and string) settle so that the string is vertical?

While riding on a bus, you place your backpack on the seat next to you. The bus is heading forward at a moderate speed when a child suddenly runs across the street in front of it. The driver slams on the brakes, stopping the bus in time to avoid the child, but your backpack moves forward off the seat and falls to the floor. Why didn't your backpack stay on the seat?

A hammer's weight acts in the downward direction, yet you can use the hammer to pound a nail into the ceiling. Why?

A melon is sitting at equilibrium in the weighing basket of a grocery store spring scale. You lift the melon upward slightly and release it. As the melon bounce up and down, the melon is accelerating upward whenever

You are bicycling up a hill at constant velocity. Neglecting any effects do to the air, in which direction is the hill's overall force on the bicycle?

A tractor is using a chain to pull a heavy log northward at constant velocity. The net force on the log

A skateboarder drops onto a steep ramp and begins to accelerate rapidly downhill along that ramp. What force is causing the skateboarder to accelerate downhill? [Neglect any effects due to friction or air resistance.]

When you catch a ball that was thrown to you by a teammate, that ball exerts a force on your hand. Can the force that the ball exerts on your hand be larger than the force your teammate exerted on the ball when throwing it?

You are walking a dog on a rope when the dog begins to chase a squirrel. You momentarily lose your grip and the rope begins to slide swiftly through your motionless hands. Why does your skin suddenly feel very hot?

You are a passenger in a car that is driving on a highway. At this moment, you are feeling both your weight downward and a weight-like sensation that points toward the right. At this moment, your

You are weighing a melon on a spring scale. The scale reports the melon's correct weight only when

You stand ready to run a long race on a level track. As the race starts, you accelerate forward. What is causing you to accelerate forward?

You drop a baseball 3 feet onto three different rigid horizontal surfaces. One surface is motionless, the second surface is moving steadily upward, and the third surface is moving steadily downward. From which surface does the ball bounce upward highest?

As they descend out of mountains, many highways have safety turnoffs to rescue trucks that have lost their brakes. A truck entering such a turnoff finds itself driving through deep sand on a gradually rising slope. Why is that arrangement better than simply stopping the truck promptly with a rigid, immovable barrier?

A soccer player kicks the ball toward the goal. After the ball leaves the player's foot and neglecting any effects due to the air, the ball experiences

Pedaling your bicycle provides power to its rear wheel and propels your bicycle forward. The bicycle's front wheel turns freely and rolls forward as the bicycle moves forward. What force(s) is principally responsible for the bicycle's forward acceleration as you pedal your bicycle forward from rest on a level (horizontal) road?

You are working in a pizza parlor. You toss a spinning disk of pizza dough into the air. As the dough stretches outward and the flying disk becomes wider, what happens to the disk's angular velocity?

A tennis racket is strung with elastic strings that store and return collision energy very well, better than a tennis ball does. How stiff should the string surface be in order to make a tennis ball bouncing off that surface travel as fast as possible?

To win a prize at the local fair, you must drop a glass marble into a glass bowl on a hard floor and that marble must come to rest in the bottom of the bowl. You try many times, but the marble keeps bouncing out of the bowl. What physics issue is preventing the marble from stopping in the bowl?