Heena Sharma, Shubhankat Vats and, Rashmi Gupta Solutions for Chapter: Motion, Exercise 6: Challengers*

Particles $\mathrm{P}$ and $\mathrm{Q}\mathrm{}$ are undergoing uniform horizontal circular motions along concentric circles of different radii in clockwise sense $\mathrm{P}$ completes each round in $2 \min$ while $\mathrm{Q}$ does it is $5 \min$ time required by $\mathrm{Q}$ to make one revolution around $\mathrm{P}$is :

You are sitting in a stationary car. There is a helium balloon tied to its floor. You accelerate and obviously feel like you are being pushed backwards (against the direction of your acceleration). The balloon :

A boy begins to walk eastward along a street in front of his house and the graph of his position from house is shown in the following figure. His average speed for whole time interval is equal to :

A bus is travelling the first one-third distance at a speed of $10 \mathrm{km} {\mathrm{h}}^{-1}$, the next one-fourth at $20 \mathrm{km} {\mathrm{h}}^{-1}$ and the remaining at $40 \mathrm{km} {\mathrm{h}}^{-1}$. What is the average speed of the bus?

A car $\mathrm{A}$ is travelling on a straight level road with a uniform speed of $60\mathrm{}\mathrm{k}\mathrm{m}/\mathrm{h}$. It is followed by another car $\mathrm{B}$. which is moving with a speed of $70\mathrm{}\mathrm{k}\mathrm{m}/\mathrm{h}$. When the distance between them is $2.5\mathrm{}\mathrm{k}\mathrm{m}$, the car $\mathrm{B}$is given a deceleration of $20\mathrm{}\mathrm{k}\mathrm{m}/{\mathrm{h}}^2$. After how much time will $\mathrm{B}$ catch up with $\mathrm{A}$?

A sprinter has to cover a total run of $100\mathrm{}\mathrm{m}$. She increases her speed from rest under a uniform acceleration of $1.\mathrm{}0\mathrm{}\mathrm{m}/{\mathrm{s}}^2$ up to three quarters of the total run and covers the last quarter with uniform speed. The time she takes to cover the first half, and to cover the second half of the run will be :

A bus begin to move with an acceleration of $1\mathrm{}\mathrm{m}/{\mathrm{s}}^2$. A man who is $48\mathrm{}\mathrm{m}$behind the bus starts running at $10\mathrm{}\mathrm{m}/\mathrm{s}$ to catch the bus. The man will be able to catch the bus after

Which graph represents a state of rest for an object?