(1) How does the work required to stretch a spring 2 cm compare with the work re
ID: 1365580 • Letter: #
Question
(1) How does the work required to stretch a spring 2 cm compare with the work required to stretch it 1 cm?
(2) A cart starting from rest rolls down a hill and at the bottom has a speed of 4 m/s. If the cart were given an initial push,so its initial speed at the top of the hill was 3 m/s, what would be its speed at the bottom?
(3) Is it possible to do work on an object that remains at rest?
(4) A ball tied to a string is being whirled around in a circle. What can you say about the work done by tension?
(5) By what factor does the kinetic energy of a car change when its speed is tripled?
Explanation / Answer
1)
as potential energy = 0.5 * k * x^2
work done to stretch the spring = 0.5 * k * x^2
work required to stretch 2 cm /work required to stretch 1 cm = 0.5 * k * 0.02^2/(0.5 * k * 0.01^2)
work required to stretch 2 cm /work required to stretch 1 cm = 4
the ratio work required to stretch 2 cm to work required to stretch 1 cm is 4 J
2)
let the speed of velocity is v
0.5 * m * v^2 = 0.5 * m * 4^2 + 0.5 * m * 3^2
v = 5 m/s
the speed at the bottom is 5 m/s
3)
as the displacement = 0 m
work done = 0 * force
work done = 0 J
4)
as the tension in perpendicular to the direction of motion
work done = F * d * cos(90)
work done = 0 J
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