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Calendar

Choose the best answer to each question and write the appropriate letter in the space below.

1) In physics, work is defined as __________.

A) force times time.
B) force divided by time.
C) force times distance.
D) force divided by distance.
E) distance divided by time. ________


2) If you lift two loads up one story, how much work do you do compared to lifting just one load up one story?
A) Four times as much
B) Twice as much
C) The same amount
D) One half as much
E) One quarter as much ________

3) If you lift one load up two stories, how much work do you do compared to lifting one load up only one story?
A) Four times as much
B) Twice as much
C) The same amount
D) One half as much
E) One quarter as much ________


4) If Nellie Newton pushes an object with twice the force for twice the distance, she does __________.
A) the same work.
B) twice the work.
C) four times the work.
D) eight times the work. ________

5) The unit of work is the __________.
A) newton.
B) watt.
C) meter.
D) joule.
E) second. ________

6) Power is defined as the __________.
A) force on an object times the distance the object moves.
B) force on an object divided by the time the force acts.
C) work done on an object divided by the time taken to do the work.
D) work done times the time taken to do that work.
E) distance divided by the time taken to move that distance. ________

7) The unit of power is the __________.
A) newton.
B) watt.
C) meter.
D) joule.
E) second. ________

8) Potential energy is the energy an object has because of its __________.
A) speed.
B) location.
C) size.
D) temperature.
E) density. ________

9) The amount of potential energy possessed by an elevated object is equal to __________.
A) the force needed to lift it.
B) the distance it is lifted.
C) the power used to lift it.
D) the work done in lifting it.
E) the value of the acceleration due to gravity. ________


10) Kinetic energy of an object is equal to __________.
A) one half the product of its mass times its speed squared.
B) one half the product of its mass times its speed.
C) its mass multiplied by its speed.
D) its mass multiplied by its acceleration.
E) its mass multiplied by its acceleration squared. _______


11) How much farther will a car traveling at 100 km/s skid than the same car traveling at 50 km/s?
A) Five times as far
B) Four times as far
C) Twice as far
D) The same distance
E) Half as far _______


12) An arrow in a bow has 70 J of potential energy. Assuming no loss of energy due to heat, how much kinetic energy will it have after it has been shot?
A) 140 J
B) 70 J
C) 50 J
D) 35 J
E) 0 J _______


13) Energy is changed from one form to another with no net loss or gain.
A) Always true
B) Sometimes true
C) Always false _______


14) As a pendulum swings back and forth __________.
A) potential energy is transformed into kinetic energy.
B) kinetic energy is transformed into potential energy.
C) at the lowest part of its swing, its energy is all kinetic.
D) at the end points of its swing, its energy is all potential.
E) all of the above _______


15) An object that has linear kinetic energy must be __________.
A) moving.
B) at an elevated position.
C) at rest.
D) none of the above _______


16) Cannonballs are launched from an airplane in the forward direction of motion. The momentum of the airplane will be __________.
A) decreased.
B) unchanged.
C) increased. _______


17) A woman can lift barrels a vertical distance of 1 meter or can roll them up a 2 meter-long ramp to the same elevation. If she uses the ramp, the applied force required is __________.
A) one quarter as much.
B) half as much.
C) twice as much.
D) four times as much.
E) the same amount. _______


18) A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of work but different amounts of __________.
A) energy.
B) power.
C) both A and B
D) none of the above _______


19) Which requires more work: lifting a 50-kg sack vertically 2 meters or lifting a 25-kg sack vertically 4 meters?
A) Lifting the 50-kg sack
B) Lifting the 25-kg sack
C) Both require the same amount of work. _______


20) A ball is thrown into the air with 100 J of kinetic energy, which is transformed to gravitational potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its kinetic energy is __________.
A) less than 100 J.
B) more than 100 J.
C) 100 J.
D) Not enough information given. _______


21) An object that has kinetic energy must be __________.
A) moving.
B) falling.
C) elevated.
D) at rest. _______


22) An object that has kinetic energy must have __________.
A) momentum.
B) acceleration.
C) a force applied to maintain it.
D) none of the above _______


23) Which has greater kinetic energy, a car traveling at 30 km/h or a half-as-massive car traveling at 60 km/h?
A) The 30-km/h car
B) The 60-km/h car
C) Both have the same kinetic energy. _______


24) A person on a roof throws one ball downward and an identical ball upward at the same speed. The ball thrown downward hits the ground with 100 J of kinetic energy. Ignoring air friction, with how much kinetic energy does the second ball hit the ground?
A) 100 J
B) 200 J
C) Less than 100 J
D) More than 200 J
E) none of the above _______


25) An object at rest may have __________.
A) speed.
B) velocity.
C) energy.
D) momentum.
E) none of the above _______


26) A heavy object and a light object are released from rest at the same height and time in a vacuum. As they fall, they have equal __________.
A) weights.
B) momenta.
C) energies.
D) all of the above
E) none of the above _______


27) If an object has kinetic energy, then it also must have __________.
A) impulse.
B) momentum.
C) acceleration.
D) force.
E) none of the above _______


28) If the velocity of a moving object doubles, then what else doubles?
A) momentum.
B) kinetic energy.
C) acceleration.
D) all of the above
E) none of the above _______


29) All simple machines ideally work on the principle that __________.
A) impulse equals momentum change.
B) force equals mass times acceleration.
C) kinetic energy transforms into potential energy.
D) total momentum before a collision equals total momentum after the collision.
E) work input equals work output. _______


30) The ratio of output force to input force of a simple machine is called the __________.
A) fulcrum.
B) pivot point.
C) efficiency.
D) mechanical advantage.
E) lever arm. _______


31) A pulley system can __________.
A) change the direction of a force.
B) multiply the force.
C) increase the amount of work done.
D) Both A and B
E) Both B and C _______


32) The ratio of useful work output to total work input is called the __________.
A) fulcrum.
B) pivot point.
C) efficiency.
D) mechanical advantage.
E) lever arm. _______


33) About how efficient is a typical gasoline-burning car engine?
A) 100%
B) 70%
C) 30%
D) 5% _______


34) A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives more change in kinetic energy is the __________.
A) small economy car.
B) limousine.
C) same for each. _______


35) A popular swinging apparatus consists of an aligned row of identical elastic balls suspended by strings so they touch each other. When two balls on one end are elevated and released, they slam into the array of balls and two balls pop out the other side. If instead, one ball popped out with twice the speed, this would be a violation of the conservation of __________.
A) momentum.
B) energy.
C) both. _______


36) Consider molecules of hydrogen gas and molecules of heavier oxygen gas that have the same kinetic energy. The molecules with more speed are __________.
A) hydrogen.
B) oxygen.
C) Both have the same speed. _______


37) How many joules of work are done on an object when a force of 10 N pushes it 5 m?
A) 50 J
B) 10 J
C) 5 J
D) 2 J
E) 1 J _______


38) How much power is required to do 100 J of work on an object in 2 seconds?
A) 200 W
B) 100 W
C) 50 W
D) 2 W
E) 0 W _______


39) How much work is done on a 50-N rock that you carry horizontally across a 10-m room?
A) 500 J
B) 50 J
C) 10 J
D) 5 J
E) 0 J _______


40) How much work is done on a 50-N rock that you lift 10 m?
A) 500 J
B) 50 J
C) 10 J
D) 1 J
E) 0 J _______


41) How much power is expended if you lift a 50-N rock 10 meters in 1 second?
A) 500 W
B) 50 W
C) 10 W
D) 5 W
E) 0 W _______


42) Suppose a moving car has 2000 J of kinetic energy. If the car's speed doubles, how much kinetic energy would it then have?
A) 8000 J
B) 6000 J
C) 4000 J
D) 2000 J
E) 1000 J _______


43) It takes 40 J to push a large box 4 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?
A) 4 N
B) 10 N
C) 40 N
D) 160 N
E) none of the above _______


44) If Kelly the skater's speed increases so he has twice the momentum, then his kinetic energy increases by __________.
A) two times.
B) four times.
C) eight times.
D) none of the above (KE remains the same.) _______


45) A 10-N object moves at 1 m/s. Its kinetic energy is __________.
A) 0.5 J.
B) 1 J.
C) 10 J.
D) more than 10 J. _______


46) A girl can easily lift an 80-N rock with the help of a lever. When she pushes down with 10 N of force, she lifts the rock 0.1 meters. How far does she move her arms to do this?
A) 10 m
B) 8 m
C) 1 m
D) 0.8 m
E) 0.1 m _______


47) A pulley has two supporting strands. In order to use it to lift a load 1 meter, the person pulling will have to pull a distance of __________.
A) 4 m.
B) 2 m.
C) 1 m.
D) 1/2 m.
E) 1/4 m. _______


48) A frictionless inclined plane is 6 m long and rests on a wall that is 2 m high. How much force is needed to push a block of ice weighing 300 N up the plane?
A) 600 N
B) 300 N
C) 200 N
D) 100 N
E) 50 N _______


49) A certain jack has a theoretical mechanical advantage of 500. However, due to frictional forces, the actual mechanical advantage is only 100. What is the efficiency of the jack?
A) 50 000
B) 500
C) 50
D) 5
E) 1/5 _______


50) A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is __________.
A) 10%.
B) 50%.
C) 90%.
D) 110%.
E) none of the above _______


Write True or False in the space provided.

51) In physics, the amount of work done on an object is the product of the force exerted on the object times the time the object moves. _______


52) The unit of work is called the joule. _______


53) The rate at which work is done is called energy. _______


54) The unit of power is the watt. _______


55) The rate at which work is done is called power. _______


56) The energy an object has by virtue of its location is its potential energy. _______


57) The energy an object has by virtue of its motion is its kinetic energy. _______


58) The ratio of output force to input force for a simple machine is its efficiency. _______


59) The ratio of useful work output to total work input is mechanical advantage. _______


60) When we carry an object across a room, without lifting it or setting it down, we do no physical work on it. _______


61) More power is needed to carry a heavy suitcase slowly up a flight of stairs than to carry the suitcase quickly up the same flight of stairs. _______


62) Energy transforms from one form to another with no net loss or gain. _______


63) A pulley system can only change direction; it can't multiply forces as well. _______


64) Using an inclined plane is an effective way to lift a heavy object that you otherwise couldn't lift. _______


On a separate sheet of paper, answer the following questions.

65) You do work on something when you lift it against gravity. How does this work relate to gravitational potential energy? If the lifted object is released, what becomes of this energy? Be sure to define all terms that you use.


66) Discuss how energy conservation applies to a pendulum. Where is potential energy the most? The least? Where is kinetic energy the most? The least? Where is the pendulum accelerating the most? The least? Where is it moving the fastest? Stopped?


67) Define a simple machine and give examples of four different ones. For each machine discuss the theoretical mechanical advantage, actual mechanical advantage, and efficiency and give numerical examples of each.


Answer the following questions in the space provided. Show all work.

68) What is the work done in lifting 50-kg of bricks to a height of 20 m?


_____________


69) What is the work done in raising a 50-kg block 3.0 m vertically ?


_____________


70) What amount of work is done on a cart that is pushed 4.0 m across a floor by a horizontal 50-N net force?


_____________


71) If possible, determine the power expended when a barbell is raised 5.0 m in 2 s.


_____________


72) A toy cart moves with a kinetic energy of 30 J. If its speed is doubled, what will its kinetic energy be?


_____________


73) In raising a 3,000-N piano with a pulley system, it is noted that for every 1 m of rope pulled down, the piano rises 0.1 m. Ideally, what force is needed to lift the piano?


_____________


74) A car traveling at 50 km/h will skid 20 m when its brakes are locked. If the same car is traveling at 150 km/h, what will be its skidding distance?


_____________


75) What amount of work can a 600-W electric drill do in 4 minutes?


_____________


76) A couch potato might consume 6 million J of energy in a day. What is this rate of energy consumption in watts?


_____________


77) A 40-kg boy runs up the staircase to a floor 5.0 m higher in 7.0 seconds. What is his power output?


_____________


78) At what height does a 1,000.0-kg mass have a potential energy of 1.0 J relative to the ground?


_____________


79) The 2.0-kg head of an ax is moving at 5.0 m/s when it strikes a log and penetrates 0.02 m into the log. What is the average force the blade exerts on the log?


_____________


80) An anvil hanging vertically from a long rope in a barn is pulled to the side and raised like a pendulum 0.80 m above its equilibrium position. It then swings to its lowermost point where the rope is cut by a sharp blade. The anvil then has a horizontal velocity with which it sails across the barn and hits the floor, 5.0 m below. How far horizontally along the floor will the anvil land?


_____________


If you have any questions, please email Ms. Cummings