Question

A body of mass 3 kg acted upon by a constant force is displaced by S metre, given by relation S = $\frac { 1 } { 3 }$t², where t is in second. Work done by the force in 2 seconds is :

• A. 8/3 J
• B. 19/5 J
• C. 5/19 J
• D. 3/8 J

Answer 1

Answer: (A)

8/3 J

Answer 2

$\frac { \mathrm { ds } } { \mathrm { dt } } = \frac { 2 } { 3 } \mathrm { t } = \mathrm { v }$ ; W = DK = K_{t = 2} – K_{t = 0}

= $\frac { 1 } { 2 } m \left( v _ { t = 2 } ^ { 2 } - v _ { t = 0 } ^ { 2 } \right)$ = $\frac { 1 } { 2 } \cdot 3 \left( \frac { 16 } { 9 } - 0 \right)$= 8/3 J