Work and energy
A 30-N box is pulled upward 6.0 m along the surface of a ramp that rises at 37° above the horizontal. How much work does gravity do on the box during this process?
-110 J
A 35 N bucket of water us lifted vertically 3 m and then returned to its original position. How much work did gravity do on the bucket during this process?
0 J
An ideal spring has a spring constant (force constant) of 60 N/m. How much energy does it store when it is stretched by 1.0 cm?
0.0030 J
A force produces power P by doing work W in a time T. What power will be produced by a force that does six times as much work in half as much time?
12 P
How much work must be done by frictional forces in slowing a 1000-kg car from 26.1 m/s to rest?
3.41 x 10^5 J
When you drop a pebble from height H, it reaches the ground with speed V if there is no air resistance. From what height should you drop it so it will reach the ground with twice speed?
4h
If 4.0 J of work are performed in stretching an ideal spring with a spring constant (force constant) of 2500 N/m, by what distance is the spring stretched?
5.7 cm
Person X pushes twice as hard against a stationary brick wall as person Y. Which one of the following statements is correct?
Both do zero work.
You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral do so Compare the gravitational potential energy of you and your friend, after you both reach stairway, taking longer to the top.
Both of you have the same amount of gravitational potential energy at the top
A truck has four times the mass of a car and is moving with twice the speed of the car. If Kt and Kc refer to the kinetic energies of truck and car respectively, it is correct to say that
Kt = 16 Kc
Two men Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do on the car
Neither of them does any work.
Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Ignoring friction and wind resistance, which one of the following statements is true?
The amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob.
If the force on an object is in the negative direction, the work it does on the object must be
The work could be either positive or negative, depending on the direction the object moves.
You throw a baseball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.
The work is negative on the way up and positive on the way down.
Jill does twice as much work as jack does and in half the time jills power output is
four times Jack 's povver output
A stone is held at a height h above the ground. A second stone with four times the mass of the first one is held at the same height. The gravitational potential energy of the second stone compared to that of the first stone is
four times as much
