Question

Velocity-time graph for a body of mass 10 kg is shown in figure. Work-done on the body in first two seconds of the motion is :

• A. 12000J
• B. -12000J
• C. -4500
• D. -9300J

Answer 1

The correct option is C -4500

[A]

$\begin{array}{c}u=50m/s\\ v=0\\ a=\frac{v-u}{t}=\frac{50}{10}=-5m/s^2\\ V=50-5t\\ att=2,v=40m/s,att=0,v=50m/s\end{array}$

Work done in first 2 seconds

$\begin{array}{c}w=\frac{1}{2}\left(10\right)\left\{v{f}^2-v{i}^2\right\}\\ w=\frac{1}{2}\times 10\left\{1600-2500\right\}=-4500j\end{array}$