Question

A 20 g particle is moving to the left at 30 m/s. A force on the particle causes it to move the the right at 30 m/s. How much work is done by the force?

Short answer

Net work done is zero.

Step-by-step solution

Given information

A 20 g particle is moving to the left at 30 m/s.

A force on the particle causes it to move the the right at 30 m/s.

Explanation

Work done by force is given by the Change in Kinetic Energy.

Lets assume

v_o be the initial velocity = -30 m/s
v₁ be the final velocity =+30 m/s

Now find the work done as Change in Kinetic Energy

W=Change in Kinetic Energy

$$\begin{gathered} W=\frac{1}{2}\times m\times \left(v_1^2-v_o^2\right) \\ W=\frac{1}{2}\times 20\times {10}^{-3}kg\times \left({(30m/s)}^2-(-30m/s{)}^2\right) \\ W=0\mathrm{J} \end{gathered}$$