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 )

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 × 105 J (B) 1.0 × 105 J (C) 1.5 J (D) 1.5 × 105 J

Tardigrade Admin · Accepted Answer

As v=u+a t ∴ 20=0+a × 10 or a=2 m s -2 Force exerted by the engine, F=m a+f=500 × 2+500 =1.5 × 103 N s=u t+(1/2) a t2=0+(1/2) × 2(10)2=102 W=F s=1.5 × 105 J

Q. A car weighing $500 k g$ 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 $g = 10 m s^{- 2}$ )

$1.05 \times 1 0^{5} J$

$1.0 \times 1 0^{5} J$

$1.5 J$

$1.5 \times 1 0^{5} J$

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

Q. A car weighing 500kg working against a resistance of 500N accelerates from rest to 20ms−1 in 10s. The work done by the engine will be (Take g=10ms−2 )

1.05×105J

1.0×105J

1.5J

1.5×105J