The linear momentum $p$ of a body varies with time and is given by the equation $p=x+y{t}^2$, where, $x$ and $y$ are constants. The net force acting on the body for a one-dimensional motion is proportional to

Two masses of $5 \mathrm{kg}$ and $10 \mathrm{kg}$ are connected to a pulley as shown. What will be the acceleration if the pulley is set free? [$g=$ acceleration due to gravity]

Two bodies of $5 \mathrm{kg}$ and $4 \mathrm{kg}$ are tied to a string as shown in the fig. If the table and pulley both are smooth, acceleration of $5 \mathrm{kg}$ body will be equal to-