Question

A car weighing $500\, kg$ working against a resistance of $500\, N$ accelerates from rest to $20\, m \,s ^{-1}$ in $10\, s$. The work done by the engine will be (Take $g=10 \,m \,s ^{-2}$ )

• A. $1.05 \times 10^{5} J$
• B. $1.0 \times 10^{5} J$
• C. $1.5 J$
• D. $1.5 \times 10^{5} J$

Answer 1

Answer: (D)

As $v=u+a t \therefore 20=0+a \times 10$
or $ a=2 m s ^{-2}$
Force exerted by the engine,
$F=m a+f=500 \times 2+500$
$=1.5 \times 10^{3} N$
$s=u t+\frac{1}{2} a t^{2}=0+\frac{1}{2} \times 2(10)^{2}=10^{2} $
$W=F s=1.5 \times 10^{5} J$