Question

The graph between the resistive force $F$ acting on a body and the distance covered by the body is shown in the figure. The mass of the body is $25\, kg$ and initial velocity is $2\, m/s$. When the distance covered by the body is $4\, m$, its kinetic energy would be

• A. 50 J
• B. 40 J
• C. 20 J
• D. 10 J

Answer 1

Answer: (D)

Initial K.E. of the body $=\frac{1}{2} m v^{2}$
$=\frac{1}{2} \times 25 \times 4=50\, J$
Work done against resistive force
$=$ Area between $F-x$ graph
$=\frac{1}{2} \times 4 \times 20=40\, J$
Final K.E. = Initial K.E. - Work done against resistive force
$=50-40=10\, J$