Show:
Work
Power
Potential Energy
Conservation of Energy
Kinetic Energy
100
Work is required to lift a barbell. How many times more work is required to lift the barbell three times as high?
Three times the original amount of work.
100
How much power is required to do 100 J of work on an object in a time of .5 s? How much power is required if the same work is done in 1 s?
200 Watts, 100 Watts
100
The equation for determing gravitational potential energy is PE=m*g*h. Which factor(s) in this equation is (are) NOT a property of an object? a) g b) h c) m d) both g and h
D) both g and h Mass is the only one of these that describe the actual object
100
If you do 100 J of work to elevate a bucket of water, what is its gravitational potential energy relative to its starting position? What about when the bucket is raised twice as high?
100 J, 200 J
100
Suppose an automobile has 2000 J of kinetic energy. When it movies at twice the speed, what will be its kinetic energy? What about three times the speed?
8000 J, 18 000 J
200
Which requires more work, lifting a 10 kg load a vertical distance of 2 m or lifting a 5 kg load a vertical distance of 4 m?
Both require the same amount of work.
200
The more powerful a motor is: a) the longer the time interval for doing work is b) the shorter the time interval for doing work is c) the greater the ability to do the work is d) the shorter workload is
B) The shorter the time interval is
200
Can the gravitational energy of an object be negative?
Yes. Potential energy is measured from a reference point. If the object is below that reference point, then the potential energy can be negative.
200
A boulder is raised above the ground so that its potential energy is 200 J. Then it is dropped. What is its kinetic energy just before it hits the ground?
200 J
200
Can the kinetic energy of an object be zero?
No. Mass is always positive and speed is squared so that will eliminate any negative values.
300
Can the speed of an object change if the net work done is zero?
No. If the net work done is zero, then there is no change in kinetic energy. Assuming the mass of the object stays constant, there is no change in speed.
300
What does the wattage of a light bulb indicate?
The wattage tells the rate at which energy is converted by the bulb.
300
An 80 kg climber with a 20 kg pack climbs 8848 m to the top of Mount Everest. What is the climber's potential energy? a) 6.94 x 10^6 J b) 4.16 x 10^6 J c) 2.47 x 10^6 J d) 1.00 x 10^6 J
A) 6.94 x 10^6 J
300
What will be the kinetic energy of an arrow having a potential energy of 50 J after it is shot from a bow?
50 Joules
300
If both the mass and the velocity of a ball are tripled, the kinetic energy of the ball is increased by a factor of: a) 3 b) 6 c) 9 d) 27
D) 27
400
A worker pushes a wheelbarrow with a horizontal force of 50 N over a level distance of 5 m. If a frictional force of 43 N acts on the wheelbarrow in a direction opposite to that of the worker, what net work is done on the wheel barrow? a) 250 J b) 0.0 J c) 35 J d) 10 J
C) 35 Joules of work
400
What is the average power supplied by a 60 kf secretary running up a flight of stairs rising vertically 4 m in 4.2 s? a) 380 W b) 560 W c) 610 W d) 670 W
B) 560 W
400
A 2 kg ball is attached to a ceiling by a 1 m long string. The height of the room is 3 m. What is the gravitational potential energy associated with the ball relative to each of the following? a) the ceiling b) the floor c) a point at the same elevation as the ball
a) -19.6 J b) 39.2 J c) 0 J
400
In what sense is energy from coal actually solar energy?
Coal is a fossil fuel, which means that it is formed from the remaints of prehistoric animals, like dinosaurs. Some dinosaurs ate plants which get their energy from the sun.
400
A 3 kg toy falls from a height of 10 m. Just before hitting the ground, what will be its kinetic energy? a) 98 J b) .98 J c) 29.4 J d) 294 J
D) 294 Joules
500
A flight attendant pulls a 50 N flight bag a distance of 250 m along a level airport floor at a constant speed. A 30 N force is exerted on the bag at an angle of 50 degrees above the horizontal. How much work is done on the flight bag? a) 12 500 J b) 7510 J c) 4820 J d) 8040 J
C) 4820 J
500
A 1000 kg sports car accelerates from rest to 25 m/s in 7.5 s. What is the average power output of the automobile engine? a) 20.8 kW b) 30.3 kW c) 41.7 kW d) 52.4 kW
c) 41.7 kW
500
A .002 kg coin, which has a zero potential energy at rest, is dropped into a 10 m well. After the coin comes to a stop in the mud, what is its potential energy? a) 0.000 J b) .196 J c) -0.196 J d) 0.020 J
C) -0.196 Joules (The coin falls below its reference point, which makes the potential energy negative)
500
A skier with a mass of 88 kg hits a ramp of snow at 16 m/s and becomes airborne. At the highest point of flight, the skier is 3.7 m above the ground. What is the skier's gravitational potential energy at this point?
3200 Joules
500
A parachutist with a mass of 50 kg jumps out of an airplane at an altitude of 1000 m. After the parachute deploys, the parachutist lands with a velocity of 5 m/s. Using the work-energy theorem, find the energy that was lost to air resistance during this jump. a) 49 300 J b) 98 000 J c) 198 000 J d) 489 000 J
D) 489 000 J