Question

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

• A. $\frac{8}{3}$J
• B. $\frac{19}{5}$J
• C. $\frac{5}{19}$J
• D. $\frac{3}{8}$J

Answer 1

Answer: (A)

$\frac{8}{3}$J

Answer 2

\ S = t²/3 \ v = $\frac{\pi}{3}$ = $\frac{2}{3}$t

at t = 0 ; v₁ = 0; t = 2s ; v₂ = $\frac{4}{3}$m/s

\ W = $\frac{1}{2}$m $(v_{2}^{2}–v_{1}^{2})$ = $\frac{1}{2}$ (3) $\left( \frac{16}{9}–0 \right)$ = $\frac{8}{3}$J