Answer to Question #180039 in Classical Mechanics for Jethro Torio

Question

A 5 kg package slides 2m down an incline of 53° above the horizontal. The coefficient of kinetic friction between package and incline is 0.4.

Calculate

a. The work done by friction on the package

b. The work done by gravity.

Answer 1

Answer

a. Friction force

F$=\mu mg sin(37°)$

=$0.4\times5\times9.8\times0.60$

=11.76N

Now friction work done

W=Fscos$\theta$

= $11.76\times2\cos180$

=-23.52J

b. Work done by gravity

W=fs cos0°

$=(mgcos 37°) \times2\times cos0°$

=$5\times9.8\times0.80\times2\times1\\78.4J$