Question

A force of 20 N acts on a body of mass 2 kg initially at rest. Find the work done in 2 s.

• A. 400 J
• B. 20 J
• C. 10 J
• D. 5 J

Hint:

\(W = \Delta KE = \dfrac{1}{2}mv^2 - \dfrac{1}{2}mu^2\). Alternatively, \(W = F \times s\) where \(s = \dfrac{1}{2}at^2\).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Work done = change in kinetic energy (work-energy theorem).
Step 2: Detailed Explanation:
\(a = F/m = 20/2 = 10\) m/s\(^2\)
\(v = u + at = 0 + 10 \times 2 = 20\) m/s
Work done \(= \dfrac{1}{2}mv^2 = \dfrac{1}{2} \times 2 \times 400 = 400\) J
Step 3: Final Answer:
Work done \(= \mathbf{400}\) J.