Problem 7-65 Energy cons. with friction - Part 4 - A
A box of apples (mass \(22\; kg\)) slides down a ramp inclined at \(44^\circ\) to the horizontal. The fiction force on the box has a magnitude of \(79\; N\). If the box starts from rest and slides \(2.5\; m\) along the ramp, determine:
(a) the work done by friction
(b) the box's final kinetic energy (using conservation of energy)
(c) the thermal energy produced.
[Ans. (a) \(-2.0\times 10^2 \;J\) (b) \(1.8\times 10^2\; J\) (c) \(2.0\times 10^2\; J\) ]
Accumulated Solution
\(W_f = fd\\ W_f = (-79 \;N)(2.4 \;m) = -2.0\times 10^2\; J\; \text{ (answer to part (a))}\)
No. \(E_f = -W_f\) The work done by friction results in mechanical energy being lost from the system.