Two coins slide horizontally off a tabletop side-by-side at the same instant and begin to fall. The US quarter was moving twice as fast as the US dime when the two coins left the tabletop. Where and when do the coins hit the level floor beneath the table? [neglect any effects due to the air.]

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

You pole vault over the bar and drop onto the giant mattress below. After bouncing a few times, you settle motionless at equilibrium on the mattress. When during your initial descent from the bar into the mattress did you reach your greatest upward acceleration?

A small airplane is anchored to the ground by a cement block. Although it's windy, friction between the block and the ground manage to prevent any movement of the block for an entire week. Finally, a huge gust of wind causes the plane to drag the block 1 meter across the parking area. During what period(s) does friction produce thermal energy and cause wear to the block?

A tractor is dragging a log across the ground in a straight line at a steady speed. Compare the force the tractor exerts on the log to the frictional force the ground exerts on the log.

To win a prize at the county fair, you must knock a massive block off a shelf. You throw two 1-kilogram balls at the block. Both balls have the same initial velocity, but one ball is "dead" and stops moving after hitting the block, while the other ball is "lively" and bounces back at the same speed it had before the bounce. Which ball transfers the largest amount of momentum to the block?

To win a prize at the county fair, you have toss a US quarter over a barrier and have it come to rest on a small glass plate. Unfortunately, the fast-moving quarter bounces repeatedly on the plate until it misses and falls to the ground. What physics issue makes it almost impossible for the quarter to stay on the plate?

Two astronauts are motionless together in deep, gravity-free space. Suddenly, the green astronaut pushes hard on the purple astronaut. While the green astronaut is pushing, which astronaut(s) is/are accelerating?

Two astronauts are motionless together in deep, gravity-free space. Suddenly, the green astronaut pushes hard on the purple astronaut. After the push, when the two astronauts are no longer touching, which astronaut(s) is/are accelerating?

A tourist is riding down Main Street in a horse-drawn wagon. The wagon is traveling in a straight line at a constant speed. What is the net force acting on the wagon? The net force is

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 left pulls especially hard on the toy and moves its end of the toy to the left. 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

Someone has filled two basketballs with water. In one ball, the water is pure so the water's rotation is almost independent of the ball's rotation. In the other ball, the water is gelled so that it must rotate with the ball. The two balls look identical and have equal weights, so how can you tell which ball contains gelled water?

When you walk onto a springboard at the diving center and settle motionless, the board will have bent downward 4 inches. You do some gentle bouncing and soon it is bent downward 8 inches (twice as far as when you were motionless). What is your acceleration when the board is bent downward 8 inches?

In which of the following four situations are you accelerating? When you are

You are pulling some children in a wagon and are about to climb a hill. There are two paths up the hill, each of which has a constant slope as it winds around the hill to the top. The steeper path is half as long as the less steep path. Compare the work you would do pulling the wagon up each path to the top of the hill. [neglect friction and any effects due to the air.]

The lid of a honey jar is stuck and you can't unscrew it by hand. You find a kitchen gadget that grips the lid tightly and provides with you with a long handle on which to push. Why does the gadget's long handle make it relatively easy to unscrew the lid?

You are the elevator operator in a retro-designed luxury high-rise apartment building. When during your vertical travels do you feel less than your normal weight? In other words, when do you feel partly weightless?

You are pulling some children in a wagon and are about to climb a hill. There are two paths up the hill, each of which has a constant slope as it winds around the hill to the top. The steeper path is half as long as the less steep path. Compare the uphill force you must exert on the wagon to keep it moving at a steady pace up each path. [neglect friction and any effects due to the air.]

Two children jump off the edge of a porch and soon land on the level ground below the porch. They jumped simultaneously and were moving at the same speed when the left the porch. However, the girl jumped horizontally forward while the boy jumped vertically upward. When and where do they land on the ground?

You are exercising on a stair machine. That machine resembles a small down escalator; it presents you with an endless series of stairs that move steadily downhill. You climb the steps but they move downward, so your altitude above the ground doesn't change much. When are you doing work on the downward-moving steps?

You are watching people step off a 20-meter cliff and fall into a deep lake. It takes a person 2 seconds of falling to reach the water. After only 1 second of falling, how high above the water is the person? [Values are approximate, so choose the closest value.]

A player kicks the soccer ball almost the entire length of the field. While the ball is traveling in an arc and touching nothing, what horizontal force does the ball experience? [neglect any effects due to the air.]

A player kicks the soccer ball almost the entire length of the field. The ball travels in an arc; it rises to peak height and then descends. Is there a time during its travel when the ball is moving fastest along the horizontal direction? In other words, is there a time when its horizontal component of velocity is greatest? [neglect any effects due to the air.]

You pole vault over the bar and drop onto the giant mattress below. After bouncing a few times, you settle motionless at equilibrium on the mattress. When during your initial descent from the bar into the mattress did you reach your greatest downward velocity?

You are roller-skating in silence with friends on a totally dark night. You are holding hands with someone, but you're not sure who it is. Fortunately, your friends have different masses. How can determine the mass of the person with whom you are holding hands?

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 downward but is accelerating steadily upward. From which surface does the ball bounce upward highest?

A bicyclist is pedaling hard and the bicycle is accelerating forward along level ground. What force is causing the bicycle to accelerate forward?

You are riding a carousel and are moving in a circular path at a constant speed. Just as you reach the northern-most point on the circular path and are heading toward the east, you accidently let go of your keys. In which direction do your keys move?

At the grocery store, you select a melon with a mass of 2 kilograms and weigh it on a spring scale. The scale reports a weight of about 20 newtons. You then take the melon and scale to Planet X, where the acceleration due to gravity is only half the Earth's acceleration due to gravity. After setting up the spring scale, you again weigh the melon. What are the melon's mass and weight on Planet X?

You are riding a roller coaster with a loop-the-loop. At this moment, you are located exactly at the top of the loop-the-loop. Although you and your car are inverted, you feel pressed into your seat. At this moment, what are your velocity and acceleration?