Newton's third law concepts

A soccer player kicks a ball with 1500 N of force. The ball exerts a reaction force against the player's foot of

• Less than 1500 N

• 1500 N

• More than 1500 N

• None of the above

An apple falls from a tree. The reaction to this is

• The Earth is pulled upward

• Air resistance on the apple

• The normal force from the ground

• None of the above

When a cannon (大砲) is fired, the accelerations of the cannon and cannonball are different because

• the forces don't occur at the same time

• the force are not the same

• the masses are different

• the ratios of force to mass are the same

A bus hits a flying bug head-on. The force smushes the bug. Which is greater, the force on the bug or the force on the bus?

• On the bug

• On the bus

• Both force are the same size

• Cannot say

Two people of equal mass on slippery (滑) ice push off each other. Will both move at the same speed in opposite directions?

• Yes

• Yes, but only if both push equally

• No

• No, unless acceleration occurs

A bird flies by

• Counteracting (抵消) the Earth's magnetic field (磁場)

• Pushing air downward so that the air pushes it upward

• Hovering (漂浮) in air

• Breathing air in and out

The scientist pushes the cart but the cart pushes back with an equal force. How does the cart move?

• The forces are balanced, so the cart does not move

• Friction with the floor is an outside force that allows the system to move

• The scientist's force is bigger than the cart's force

• Air resistance pushes the cart forward