Question

A force of 5 N acts on a 15 kg body initially at rest. The work done by the force during the first second of motion of the body is

• A. 5 J
• B. $\frac { 5 } { 6 } J$
• C. 6 J
• D. 75 J

Answer 1

Answer: (B)

$\frac { 5 } { 6 } J$

Answer 2

$W = F s = F \times \frac { 1 } { 2 } a t ^ { 2 }$ $\left[ \operatorname { from } s = u t + \frac { 1 } { 2 } a t ^ { 2 } \right]$

⇒ $W = F \left[ \frac { 1 } { 2 } \left( \frac { F } { m } \right) t ^ { 2 } \right]$