Question

A 10-N force is applied to push a block across a frictional surface at constant speed for a displacement of 5.0 m to the right. What is the work done by each force?

Answer 1

Given that the force applied is

`F_(app)=10\text{ N}`

The displacement is towards the right is d = 5 m

We have to find

(a) The work done due to applied force.

(b) The work done due to frictional force.

(c) The work done due to normal force.

(d) The work done to force of gravity.

(a) The work done due to applied force will be

`\begin{gathered} W_(app)=10*5*\cos 0^(\circ) \\ =50\text{ J} \end{gathered}`

As the direction of force and displacement is the same, so work done will be positive.

(b) The work done due to frictional force will be

`\begin{gathered} W_(fric)=(F_(fric)* d)*\cos 180^(\circ) \\ =10*5*-1 \\ =-50\text{ J} \end{gathered}`

As the direction of force and displacement are opposite.

(c) The work done due to normal force will be

`\begin{gathered} W_(normal)=F_(normal)* d*\cos 90^(\circ) \\ =20\text{ }*5*0 \\ =\text{ 0 J} \end{gathered}`

(d) The work done due to gravitational force is

`W_(grav)=F_(grav)*\text{ d}*\cos 90^(\circ)`

W_grav = F_grav x d x cos 90 degrees.

= 20 x 5 x 0

= 0 J