Question

A body is pushed through a distance of 5 m with constant velocity across a surface offering 75 N resistance. The work done by the applied force is

• A. 700J
• B. -700J
• C. -375J
• D. 375J

Answer 1

The correct option is D 375J

Friction force acting on the body, f = –75 N
(Negative sign shows that the friction force acts in the opposite direction of motion of the body)To overcome the frictional force f, same amount of force is to be applied in the opposite direction, so that the body will move with uniform velocity.Let the external force be F.$\Rightarrow F=75N(\because F=–f=–(–75\left)N\right)Displacement,s=5mAnglebetweenFands,\theta =0^{\circ }Workdone,W=Fscos\theta \Rightarrow W=75\times 5\times cos{0}^{\circ }=75\times 5\times 1(\because cos{0}^{\circ }=1)\Rightarrow W=375J$