Question

A body of mass 5 kg is moving with a momentum of 10 kg-m/s. A force of 0.2 N acts on it in the direction of motion of the body for 10 seconds. The increase in its kinetic energy is

• A. 2.8 J
• B. 3.2 J
• C. 3.8 J
• D. 4.4 J

Answer 1

Answer: (D)

4.4 J

Answer 2

Change in momentum $= P _ { 2 } - P _ { 1 } = F \times t$ ⇒

$P _ { 2 } = P _ { 1 } + F \times t = 10 + 0.2 \times 10 = 12 \mathrm {~kg} - \mathrm { m } / \mathrm { s }$Increase in kinetic energy $E = \frac { 1 } { 2 m } \left[ P _ { 2 } ^ { 2 } - P _ { 1 } ^ { 2 } \right]$