Question

For how long should a force of 100 N act on a body of 20 kg so that it acquires a velocity of 100 m/s?

Answer 1

We are going to find acceleration
Force = mass × acceleration
$$\begin{gathered} 100=20\times a \\ \Rightarrow a=\frac{100}{20} \\ \Rightarrow a=5 \end{gathered}$$
Now, putting these values in the equation:
$$\begin{gathered} v=u+at \\ \Rightarrow 100=0+5\times t \\ \Rightarrow 100=5t \\ \Rightarrow t=20 \end{gathered}$$
So, the required time is 20 s.