Question

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

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

Answer 1

The correct option is C $\frac{5}{6}J$

Initial speed $u=0$

Acceleration $a=\frac{F}{m}=\frac{5}{15}=\frac{1}{3}m/s^2$

Distance covered in one second $S=ut+\frac{1}{2}a{t}^2$

where $t=1s$

Or, $S=0+\frac{1}{2}\left(\frac{1}{3}\right)(1{)}^2=\frac{1}{6}m$

Work done $W=FS=5\times \frac{1}{6}=\frac{5}{6}J$