A body of mass 2 kg starts from rest and moves with uniform accleration. If it acquires a velocity of 20 ms^–1 in 4s, the power consumed in two seconds is

Given,

Mass m = 2kg

initial velocity u =0m/s

final velocity v = 20m/s

time t= 4s

Here acceleration,

$$\begin{gathered} v=u+at \\ \Rightarrow a=\frac{v-u}{t} \\ \Rightarrow a=\frac{20}{4}=5m/s^2 \end{gathered}$$

Now the force,

$$\begin{gathered} \mathrm{Force}=\mathrm{mass}\times \mathrm{acceleration} \\ \Rightarrow \mathrm{F}=2\times 5=10\mathrm{N} \end{gathered}$$

The displacement is,

$$\begin{gathered} s=ut+\frac{1}{2}a{t}^2 \\ \Rightarrow s=0+\frac{1}{2}\times 5\times 16=40m \end{gathered}$$

Work done is,

$\mathrm{Work} \mathrm{done} = \mathrm{force}\times \mathrm{displacement}$

$W=F\times s=10\times 40=400J$

The power is

$Power=\frac{work}{time}=\frac{400}{2}=200watt$

Hence the correct answer is 200W.