Unformatted text preview: e ladder, what The same equations apply as in part (a), together with
and the vertical
equilibrium condition
Then
(0.250) (124 lb) = 31.0 lb. Now is
unknown, and satisfies 3 Problem 3: [12pt] A ball of mass
kg is dropped from
a height
m above a large spring with spring constant
600 N/m.
(a) [6pt] What is the total work done on the ball during the
spring’s compression, from the time it contacts the spring to the
time it momentarily comes to rest? Include the correct sign. The work done on the ball is its change in kinetic energy,
By energy conservation, the kinetic energy
of the ball at the top of the spring is
Therefore, (b) [6pt] Find the maximum compression distance of the spring before it rebounds. The ball’s kinetic energy when it reaches the spring is
When it stops, it has
only potential energy. Taking the gravitational potential energy to be zero at the top of
the spring, this potential energy can be expressed in terms of the compression as Energy conservation then gives Numerically, if which implies that is measured in meters, this gives Then Only the positive value is a compression, so 0.695 m = 69.5 cm....
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 Fall '12
 ScottYost
 Physics, Force, Friction, m/s, ball, goal post

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