NCERT Solutions for Chapter: Laws of Motion, Exercise 1: MCQ-I

A meter scale is moving with uniform velocity. This implies

 A cricket ball of mass $150 \mathrm{g}$ has the initial velocity$\overrightarrow{u}=(3\hat{\mathit{i}}+4\hat{\mathit{j}}) \mathrm{m} {\mathrm{s}}^{-1}$ and a final velocity $\overrightarrow{v}=-(3\hat{i}+4\hat{\mathit{j}}) \mathrm{m} {\mathrm{s}}^{-1}$ after being hit. The change in momentum (final momentum - initial momentum) is (in $\mathrm{kg} \mathrm{m} {\mathrm{s}}^{-1}$ )

A cricket ball of mass $150 \mathrm{g}$ has an initial velocity $u=(3i+4j) \mathrm{m} {\mathrm{s}}^{-1}$ and a final velocity $v=-(3i+4j) \mathrm{m} {\mathrm{s}}^{-1}$ after being hit. The magnitude of momentum transferred during the hit is:

Conservation of momentum is a collision between particles can be understood from

 A hockey player is moving northward and suddenly turns westward with the same speed to avoid an opponent. The force that acts on the player is:

A body of mass $2 \mathrm{kg}$ travels according to the law $x\left(t\right)=pt+q{t}^2+n{t}^3$, where $p=3 \mathrm{m} {\mathrm{s}}^{-1},q=4 \mathrm{m} {\mathrm{s}}^{-2}$ and $n=5 \mathrm{m} {\mathrm{s}}^{-3}$. The force acting on the body at $\mathrm{t}=2$ seconds is:

A body of mass $5 \mathrm{kg}$ is acted upon by a force $\overrightarrow{F}=(-3\hat{i}+4\hat{\mathit{j}}) \mathrm{N}$. If its initial velocity at $t=0$ is $\overrightarrow{v}=(6\hat{i}-12\hat{j}) \mathrm{m} {\mathrm{s}}^{-1}$ the time at which it will just have a velocity along the $y$axis is:

A car of mass $m$ starts from rest and acquires a velocity along east $\overrightarrow{v}=v\hat{i}(v>0)$in two seconds. Assuming the car moves with uniform acceleration, the force exerted on the car is: