Question

A block of mass m 5

2.50 kg is pushed a distance

d 5 2.20 m along a frictionless

horizontal table by a constant

applied force of magnitude

F 5 16.0 N directed at an angle

u 5 25.0° below the horizon-

tal as shown in Figure P5.8.

Determine the work done by (a) the applied force, (b) the normal force exerted by the table, (c) the force of gravity, and (d) the net force on the block

Answer 1

$m=2.50 kg$

$d=2.20m$

$F=16.0N$

$\alpha=25.0°$

(a)

$W=F\cdot d\cdot \cos \alpha =16\cdot 2.2\cdot \cos 25°=31.9J$

(b) The normal force is perpendicular to the displacement of the block. So,

$W_N=F_N\cdot d\cdot \cos \alpha =F_N\cdot d\cdot \cos 90°=0J$

(c) Gravity force is also perpendicular to the displacement. So,we have

$W_G=F_G\cdot d\cdot \cos \alpha =F_G\cdot d\cdot \cos 90°=0J$

(d)

$W_\Sigma=W+W_N+W_G=31.9+0+0=31.9J$