Physics Ch. 5

The length of a force vector indicates the
a. direction of force
b. magnitude of force

Action: Earth pulls on moon
Reaction: ?
a. moon pulls on earth
b. moon pushes on earth
c. moon pulls on sun
d. earth pushes on moon

Which force is greater, earths pull on moon or moon’s pull on earth?
a. both pulls are the same
b. earth’s
c. moon’s

If the cannon’s recoil is the result of an equal and opposite reaction, why is the cannon’s acceleration lower than the shell’s acceleration?
a. The cannon’s acceleration is not lower than the shell’s acceleration; it has the same acceleration as the shell
b. the cannon has more mass than the shell
c. not as much force is applied to it

Since movement of an object or system requires that a net force be applied to it, how can this occur if all action forces have opposite and equal reaction forces?
a. the action force doesn’t act on the same object as the reaction force
b. sometimes there are singular, unpaired forces acting on an object
c. newton was never able to explain this

What allows a horse to accelerate forward even though a cart is pulling back on the horse?
a. Friction from the ground on the horse is stronger than the sideways force the horse is exerting on the ground.
b. The horse is pulling on the cart with a stronger force than the cart is pulling back on the horse.
c. The force of friction the ground exerts on the horse is larger than the force the cart is pulling back on the horse.

Which of the following is NOT a statement or consequence of Newton’s third law?
a. there can never be only one force acting on an object
b. all the forces come in pairs
c. no forces can exist on its own
d. every force has an opposite and equal reaction

Give an example of a vector and scalar

An archer shoots an arrow. Consider the action force to be the bowstring against the arrow. The reaction to this force is the
a. grip of the archer’s hand on the bow
b. combined weight of the arrow and bowstring
c. friction of the ground against the archer’s feet
d. air resistance against the bow
e. arrow’s push against the bowstring

A player catches a ball. Consider the action force to be the impact of the ball against the player’s glove. The reaction to this force is the
a. friction of the ground against the player’s shoes
b. player’s grip on the glove
c. force the glove exerts on the ball
d. muscular effort in the player’s arm
e. none

The attraction of a person’s body toward earth is called weight. The reaction to this force is
a. the person’s body pushing against earths surface
b. the persons body pulling on the earth
c. the earth’s surface pushing against the person’s body
d. none

A skydiver falls towards the Earth. The attraction of the Earth on the diver pulls the diver down. What is the reaction to this force?
a. water resistance that will soon act upward on the diver
b. the attraction to the planets, stars, and every particle in the universe
c. air resistance the diver encounters while falling
d. all of the above
e. none of the above

Two people, one twice as massive as the other, attempt a tug-of-war with 12 meters of massless rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of
a. 0 m
b. 4 m
c. 6 m
d. 3 m

A piece of rope is pulled by two people in a tug-of-war. Each pulls with 400 N of force. What is the tension in the rope
a. 600 N
b. 0
c. 400 N
d. 800 N

The force exerted on the tires of a car to directly accelerate it along a road is exerted by the
a. tires
b. air
c. road
d. engine
e. none

A vehicle that weighs 4000 N on the surface of the Earth is travelling in outer space at a speed of 200 m/s. The smallest constant force that must be applied to stop it in 20 seconds is
a. 4000 N
b. 400 N
c. 40 N
d. more than 4000 N
e. 20 N

A vehicle that weights 400 N on the surface of the Earth is traveling in outer space at a speed of 400 m/s . It can be stopped by applying a constant force of 20 N for
a. 4 sec
b. 2 sec
c. 400 sec
d. 800 sec
e. 80 sec

What is the formula for two resultant vectors?

Arnold Strongman and Suzie Small each pull very hard on opposite ends of a massless rope in a tug-of-war. The greater force on the rope is exerted by
a. arnold, of course
b. suzie, surprisingly
c. both the same

A bird sitting on the limb of a tree is moving about 30 km/s with respect to the sun. If the bird takes 1 second to drop down to a worm below, the worm would be 30 km downrange from the bird when it reached the ground. This faulty reasoning is best countered with Newton’s
a. first law
b. second law
c. law of gravitation
d. third law