physics 107 test 2

Two billiard balls of the same mass roll straight toward each other. The first has a velocity of +5 m/s and the second has a velocity of -3 m/s. Aer colliding, the first ball has a velocity of A -3 m/s. B +3 m/s C -5 m/s. D +5 m/s. E. +2 m/s.

a. -3 m/s

A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground? A 80 J B 6 J C 8 J D 32 J E none of these

a. 80 J

An upright broom is easier to balance when the heavier end is A highest, farthest from your hand. B nearest your hand. C same either way.

a. highest, farthest from your hand

A heavy truck and a light truck roll down a hill. Neglecting friction, at the bottom of the hill, the light truck will have less A momentum. B speed. C acceleration. D all of these. E none of these.

a. momentum

Your pet hamster sits on a spinning record player. If the angular speed of the record player doubles and he moves to a point twice as far from the center, then his linear speed A quadruples. B doubles. C remains the same. D halves. E is one fourth as much.

a. quadruples

A jack system will increase the potential energy of a heavy load by 400 J and generate 600 J of heat with a work input of 1000 J. The efficiency of the jack system is A 25%. B 40%. C 60%. D 100%. E Not enough information is given.

b. 40%

To do 10 J of work pushing a crate using 2 N of force, you will need to push the crate A 0.2 m. B 5m. C 10 m. D 20 m.

b. 5 m

How long will it take to stop a 1500 kg car moving at 20 m/s with a braking force of 6000 N? A 0.2 s B 5 s C 50 s D 80 s

b. 5 s

Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr? A the 30 km/hr car B the 60 km/hr car C Both have the same kinetic energy. D More information is needed about the distance traveled.

b. 60 km/hr car

Acrobat Bart at the circus drops vertically onto the end of a see -saw, with his partner Art equidistant from the fulcrum at the other end. Art is propelled straight upward a distance twice that of Bartʹs dropping distance. Neglecting inefficiencies we see A the masses of Art and Bart are equal. B Art has half the mass of Bart. C Bart has half the mass of Art. D need more information

b. Art has half the mass of Bart

A simple lever, properly arranged, is capable of multiplying work input. A sometimes true B always false C always true

b. always false

A car travels in a circle with constant speed. The net force on the car is A directed forward, in the direction of travel. B directed towards the center of the curve. C zero because the car is not accelerating. D none of these

b. directed towards the center of the curve

Centrifugal forces are an apparent reality to observers in a reference frame that is A at rest. B rotating. C an inertial reference frame. D moving at constant velocity. E none of these

b. rotating

Which requires the most amount of work by the brakes of a car? A slowing down from 70 km/h to a stop B slowing down from 100 km/h to 70 km/h C equal amounts for either

b. slowing down from 100 km/h to 70 km/h

If you need to tighten a bolt with 80 Nm of torque using a wrench with a handle that is 25 cm from the axis of the bolt, how much force do you need to apply when turning the wrench? A 20N B 80N C 320 N D 2000 N

c. 320 N

A heavy truck and a light truck roll down a hill. Neglecting friction, at the bottom of the hill, the heavy truck will have greater A acceleration. B speed. C momentum.

c. momentum

When a twirling ice skater brings her arms inward, her angular momentum A decreases. B increases. C remains the same.

c. remains the same

A ring, a disk, and a solid sphere begin rolling down a hill together. The one to reach the bottom last is the A disk. B sphere. C ring. D They all reach the bottom at the same time.

c. ring

The center of mass of a human body is located at a point A which is fixed, but different for different people. B that is always directly behind the belly button. C that changes as a person bends over.

c. that changes as a person bends over

How can you increase the angular momentum of a ball spinning on a string? A increase the length of the string B spin the ball faster C spin the ball for a longer time D A) and B) E all of the above

d. A (increase the length of the string) and B (spin the ball faster)

The famous Leaning Tower of Pisa doesnʹt topple over because its center of gravity is A displaced from its center. B in the same place as its center of mass. C relatively low for such a tall building. D above a place of support. E stabilized by its structure.

d. above a place of support

Doing twice the usual work on an object in four times the usual time requires A eight times the usual power. B twice the usual power. C the usual power. D one half the usual power. E one eighth the usual power.

d. one half the usual power

A 1-kg glider and a 3-kg glider both slide toward each other at 2 m/s on an air track. They collide and stick. The combined mass moves at A 0 m/s. B 1/2 m/s. C 1/3 m/s. D 1/6 m/s. E 1 m/s.

e. 1 m/s

A longer cannon barrel is advantageous because it increases A impulse delivered to the ball by allowing the force to be applied for a longer time. B impulse delivered to the ball by applying a larger force. C the ball's momentum is increased by its velocity. D A and B. E A and C.

e. A (impulse delivered to the ball by allowing the force to be applied for a longer time.) and C (the ball's momentum is increased by its velocity.)

When a car is braked to a stop, its kinetic energy is transformed to A energy of motion. B energy of rest. C potential energy. D stopping energy. E heat.

e. heat