The graph of potential energy $U(x)$ versus distance $x$ is shown in the following figure. The force $F$ versus distance $x$ graph will be represented by (assume, that the force is conservative)

The block starts from rest as shown in the figure. Find the work done by force of 10 N and friction in the time 0 to 4 s . [Take, $g=10 \mathrm{~m} / \mathrm{s}^2$ ]

Under action of force, a 2 kg body moves such that its position $x$ as function of time $t$ is given by $x=\alpha t^2 / 2$, where $x$ is in metre, $t$ is in seconds and $\alpha=1 \mathrm{~m} / \mathrm{s}^2$. The work done by the force in the first two seconds is

A force of 4 N acts on a 10 kg body initially at rest. Let $W_1$ is work done by force during $0 \leq t \leq \mathrm{ls}$. Likewise $W_2$ is the work done by force during $\mathrm{l} \mathrm{s} \leq t \leq 2 \mathrm{~s}$, where $t$ is time in second. The ratio $\frac{W_2}{W_1}$ is