A boy pushes a heavy door with his hand and it swings open. His hand exerts a forward force on the door. Which force is the partner to that force?

A book lies still on a table, and the table pushes upward on the book. Which force is the partner to the table's upward push on the book?

A batter's bat strikes a baseball and sends it toward the outfield. The bat exerts a forward force on the ball. What is the partner to that force?

An apple falls from a branch because Earth pulls it downward with gravity. Which force is the partner to Earth's gravitational pull on the apple?

A car speeds up as its driven tires push backward on the road surface. Which force partners with the tires' backward push on the road?

A magnet lying on a desk attracts a steel paperclip toward it. Which force is the partner to the magnet's pull on the paperclip?

At a fair, Maya's bumper car strikes Leo's car from behind and pushes it forward. Which force is the partner to Maya's car pushing Leo's car forward?

A student on roller skates pushes forward against a gym wall and rolls backward across the floor. Which force is the partner to her push on the wall?

A horse pulls a loaded cart forward along a road, exerting a forward pull on the cart. What is the partner to that pull?

In a tug-of-war, Ana pulls the rope toward her team. Which force is the partner to Ana's pull on the rope?

A shopper's hands exert a forward force on a cart handle as she pushes the cart across a parking lot. Which force is its partner?

A woodpecker's beak strikes the bark of a tree trunk. The beak exerts a force on the trunk. Which force is the partner to it?

A 12,000 kg truck and a 1,200 kg car collide head-on. During the collision, how do the forces the two vehicles exert on each other compare?

During a collision, a 1,400 kg van pushes on a 700 kg car with a force of 8,000 N. How large is the force the car pushes back on the van?

A heavy bowling ball knocks over a light pin. A student claims the ball pushed harder on the pin than the pin pushed on the ball. What corrects this claim?

Two identical 0.50 kg carts roll toward each other on a smooth track and collide head-on. How do the changes in their motion compare?

On a low-friction track, a 2.0 kg cart rolls into a stationary 0.50 kg cart. Force sensors record the force on each cart during contact. What do the sensors show?

A hailstone strikes the windshield of a parked car and cracks the glass. How does the hailstone's force on the glass compare with the glass's force on the hailstone?

A freight train strikes a stalled car at a crossing and barely slows down. What can you conclude about the sizes of the two forces during the impact?

During a tackle, a 110 kg linebacker and a 70 kg receiver push on each other with equal and opposite forces. Why don't these two forces cancel out?

In deep space, a 300 kg probe collides with a 30,000 kg asteroid. With no air and no surface underneath, how do the collision forces compare?

Workers cover a wall with thick foam before a 600 kg wrecking ball swings into it. How does the foam change the collision?

A 1,000 kg car and a 3,000 kg truck collide and push on each other with equally strong forces. Whose motion changes more during the collision, and why?

In a crash, each vehicle experiences a 12,000 N force. The car has a mass of 1,000 kg and the truck 3,000 kg. What is the car's acceleration?

A bus and an insect exert equal forces on each other during an impact. Why is the insect destroyed while the bus is unaffected?

A 0.50 kg cart and a 2.0 kg cart are pushed apart by a released spring, which pushes each with an equal force. How do their speeds compare afterward?

A 40 kg skater and an 80 kg skater push off each other on smooth ice. Which skater ends up moving faster, and why?

A golf club and a golf ball push on each other with equal forces during contact. Why does the ball fly away while the club barely slows?

A falling apple and Earth pull on each other with equal gravitational forces. Why does the apple visibly speed up while Earth's motion is not noticeable?

Two bumper cars collide. The car carrying two riders has twice the total mass of the other. Whose velocity changes more during the collision?

Two carts collide, and each experiences a 6.0 N force. Cart A has a mass of 0.50 kg and cart B has a mass of 3.0 kg. How does cart A's acceleration compare?

A tennis ball and a bowling ball collide. The tennis ball pushes on the bowling ball for 0.01 s. For how long does the bowling ball push on the tennis ball?

A spacecraft far from any planet fires its engine and speeds up, even though there is no air around it to push against. What pushes the spacecraft forward?

A swimmer sweeps her arms to push pool water backward, and she moves forward. What pushes the swimmer forward?

A student walking down a hallway pushes his shoes backward against the floor with each step. What pushes him forward?

A cannon mounted on a ship's deck rolls backward the instant it fires a heavy shell forward. What makes the cannon move backward?

An inflated balloon is released and darts across the room as air rushes out of its neck. What pushes the balloon forward?

A squid squirts a jet of water backward and shoots forward through the ocean. What pushes the squid forward?

A rower pulls the oar blades backward through the water, and the boat moves forward. What pushes the boat forward?

A helicopter hovers in place while its rotor blades drive air downward. What holds the helicopter up?