Question

How much work must be done by a force on 50 kg body in order to accelerate it from rest to 20 $m{s}^{-1}$ in 10 s

• A. $10^{3}J$
• B. $10^{4}J$
• C. $2\times 10^{3}J$
• D. $4\times 10^{4}J$

Answer 1

Answer: (B)

Final velocity v = u + at
$\therefore$ $20=0+a\times 10$ or
$20=a\times 10$ or
$a=2m{s}^{-2}$ now
$s=ut+\frac{1}{2}a{t}^2$
or $s=0+\frac{1}{2}\times 10\times 10\times$ or s=100m
$\therefore$ work done W = F $\times$ s or W = ma $\times$ s
$\therefore$ $W=50\times 2\times 100orW=10000$
$=10^{4}J$