Physics 102- HW 5

A bullet fired horizontally over level ground hits the ground in 0.5 second. If it had been fired with twice the speed in the same direction, it would have hit the ground in A. less than 0.5 s. B. more than 0.5 s. C. 0.5 s. D. not enough information.

C. 0.5 s

A gun with a muzzle velocity of 100 m/s is fired horizontally from a tower. Neglecting air resistance, how far downrange will the bullet be 1 second later? A. 50 m B. 98 m C. 100 m D. 490 m E. 49 m

C. 100 m

A 1000-kg car and a 2000-kg car are hoisted the same distance. Raising the more massive car requires A. less work. B. the same amount of work. C. twice as much work. D. four times as much work. E. more than four times as much work.

C. twice as much work

If an object's speed is doubled, its kinetic energy is A. the same B. doubled. C. tripled. D. quadrupled. E. halved.

D. quadrupled

Negative work means A. the kinetic energy of the object increases. B. nothing; there is no such thing as negative work. C. the object has negative velocity. D. the kinetic energy of the object decreases. E. the object does not move.

D. the kinetic energy of the object decreases

A 1486 kg car accelerates at a rate of ______ m/s/s over a distance of ______ m. What is the work done in Joules to accelerate the car?

______________ J

A refrigerator is pushed a distance of _____ m with a force of _____ N. How much work in Joules is done on the set?

______________ J

A ball player wishes to determine pitching speed by throwing a ball horizontally from an elevation of ___ m above the ground. The player sees the ball land ____ m down range. What is the player's pitching speed in m/s?

________________ m/s

A bullet is fired horizontally with an initial velocity of _____ m/s from a tower ___ m high. If air resistance is negligible, what is the horizontal distance the bullet travels before hitting the ground?

__________________ m

A hunter on level ground fires a bullet at an angle of 10 degrees above the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first? A. The dropped one. B. The fired one. C. Both hit at the same time. D. Not enough information to determine.

A. The dropped one

True or False: Two identical projectiles are launched with equal speeds from the top of a building and feel no air resistance. Projectile A is launched above the horizontal while projectile B is launched below the horizontal. Both projectiles have exactly the same acceleration while they are in the air. A. True B. False

A. True

If you push for a half hour or a whole hour against a stationary wall A. no work on the wall is done in either case. B. half as much work is done during the half hour. C. twice as much work is done during the half hour. D. it is impossible to determine how much work is done.

A. no work on the wall is done in either case

The weight of objects on the moon is 1/6 of their weight on earth. A golf ball moving with speed v on the moon has kinetic energy equal to __________________ it would have if it was moving at the same speed on earth. A. the kinetic energy B. 1/36 the kinetic energy C. 1/6 the kinetic energy D. 6 times the kinetic energy E. 36 times the kinetic energy

A. the kinetic energy

True or False: A grasshopper leaps into the air at a 62 degree angle above the horizontal. At its highest point, the grasshopper's velocity and acceleration are equal to zero. A. True B. False

B. False

A hunter on level ground fires a bullet at an angle of 2 degrees below the horizontal while simultaneously dropping another bullet from the level of the rifle. Which bullet will hit the ground first? A. The dropped one. B. The fired one. C. Both hit at the same time. D. Not enough information to determine.

B. The fired one

Energy of motion is __________ energy.

Kinetic

True or False: Kinetic energy is proportional to the square of an object's velocity. True False

True

A fast marathon runner can run the _____ km distance in _____ hours. If the runner's mass is _____ kg, and she runs at a constant speed, what was her kinetic energy in Joules during the race?

_____________ J

It takes _____J to push a heavy chair ______ m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box in Newtons?

_____________ N

A stone is thrown horizontally from the top of a cliff. One second after it has left your hand, its vertical distance below the top of the cliff is A. 5 m. B. 10 m. C. 15 m. D. 20 m. E. none of the above.

a. 5 m