Question

A 36.5 kg box initially at rest is pushed 4.25 m along a rough, horizontal floor with a constant applied horizontal force of 150 N. If the coefficient of friction between box and floor is 0.300, find the following.

(a) the work done by the applied force
J

(b) the increase in internal energy in the box-floor system due to friction
J

(c) the work done by the normal force
J

(d) the work done by the gravitational force
J

(e) the change in kinetic energy of the box
J

(f) the final speed of the box
m/s

Answer 1

(a) the work done by the applied force

150*4.25 = 637.5 J

(b) the increase in internal energy in the box-floor system due to friction

0.300*36.5*9.8*4.25 = 456 J

(c) the work done by the normal force

= 0 J as no displacement is taking place in that direction

(d) the work done by the gravitational force

0 J, as there is zero displacement in that direction too.

(e) the change in kinetic energy of the box

637.5 - 456 J = 181.5 J

(f) the final speed of the box

0.5*36.5*v^2 = 181.5 J or v v = 3.15 m/s