Newton's second law

  1. A certain motor can produce a force of 70 N on a model plane. If the required acceleration is
    30 m/s2, then what is the maximum mass the plane can have?
  1. A car has a mass of 2,000 kg. How much force is required to stop the car in 4.0 seconds from a speed of 20 m/s?
  1. What is the acceleration of a 100 kg object that experiences a net force of -10 N?
  2. How much force is required to accelerate a 0.10-gram mosquito at 20 m/s2?
  1. The position vs. time graph below corresponds to motion with which of the following characteristics?

A.  Positive initial velocity and positive force.

B.  Positive initial velocity and negative force.

C.  Negative initial velocity and positive force.

D.  Negative initial velocity and negative force.

  1. A car accelerates from rest to 30 m/s in 6.0 seconds. What is the net force on the car?
  1. A net force of 10 N acts upon a 1.0 kg cart on a straight track. Label each statement below as true, possibly true, or false.
  1. The cart moves with a constant velocity.
  2. The cart moves with a constant acceleration.
  3. The cart speeds up.
  4. The cart slows down.

Newton’s third law

1.  Explain what is meant by the statement “A single force cannot exist.”

2.  A jet liner strikes a hummingbird during takeoff. Which is bigger: the force the jet liner exerts on the hummingbird, or the force the humming bird exerts on the jet liner?

3.  A basketball player dribbles a ball. The ball exerts a force on the floor with each impact. What is the reaction force?

A.  The ball attracts the Earth.

B.  The ball rebounds upward.

C.  The floor pushes up on the ball.

D.  Molecular bonds hold the floor together.

4.  Identify the reaction force:

a.  A hammer puts a force on a nail.

b.  A man pushes a sofa across the floor.

c.  A magnet attracts a compass needle.

d.  A girl hauls up on a bucket of water.

e.  A fan pushes air into the room.

f.  Friction slows down a skidding car.

5.  A soccer ball in free-fall from the instant after it is kicked until it hits the ground. During free-fall, the force of gravity acts on the ball. What is the reaction force to the force of gravity?

A.  no reaction force exists

B.  the ball pulling up on the Earth

C.  air resistance on the ball

D.  the upward component of the kicking force.

E.  the force of the ball on the foot.

6.  A 500-gram puck and a 250-gram puck collide on a frictionless air table. During the collision, the 250-gram puck undergoes an acceleration of 4.0 m/s.

a.  What force acts on the 250-gram puck?

b.  What force acts on the 500-gram puck?

c.  What is the acceleration of the 500-gram puck?

7.  Two identical bumper cars initially traveling at different speeds undergo a head-on collision. Which quantities must be equal in magnitude?

a.  the collision force on each car (yes) (no)

b.  their accelerations during the collision (yes) (no)

c.  their final velocities (yes) (no)

8.  A student stands in the cafeteria line. His weight force down and the normal force acting upward on him are equal and opposite forces, but they are not an action and reaction pair. Why not? Give two reasons.

9.  Sketch the action and reaction forces for these situations on the outlines below each figure.

a.  A locomotive pulls a boxcar to the right. b. A tugboat pushes a barge to the right.

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