Question

A body of mass 2 Kg starts from rest and moves with uniform acceleration. It acquires a velocity 20 m/in 4s. The power exerted on the body in 2s in watts is:

• A. 50 watt
• B. 100 watt
• C. 150 watt
• D. 200 watt

Answer 1

The correct option is D 200 watt

Given that,

Mass $m=2kg$

Initial velocity $u=0m/s$

Final velocity $v=20m/s$

Time $t=4s$

Now, the acceleration is

$v=u+at$

$a=\frac{v-u}{t}$

$a=\frac{20}{4}$

$a=5m/s^2$

Now, the force is

$F=ma$

$F=2\times 5$

$F=10N$

Now, the displacement is

$s=ut+\frac{1}{2}a{t}^2$

$s=0+\frac{1}{2}\times 5\times 16$

$s=40m$

Now, the work done is

$W=F\cdot s$

$W=10\times 40$

$W=400J$

Now, the power is

$P=\frac{W}{t}$

$P=\frac{400}{2}$

$P=200watt$

Hence, the power is $200watt$