NCERT Solutions for Chapter: Motion in a Straight Line, Exercise 4: SA

A bird is tossing (flying to and fro) between two cars moving towards each other on a straight road. One car has a speed of $18 \mathrm{km}/\mathrm{hr}$ while the other has the speed of $27 \mathrm{km}/\mathrm{hr}$. The bird starts moving from the first car towards the order and is moving with the speed of $36 \mathrm{km}/\mathrm{hr}$ and when the two cars were separated by $36 \mathrm{km}$. What is the total distance covered by the bird? What is the total displacement of the bird?

A man runs across the roof-top of a tall building and jumps horizontally with the hope of landing on the roof of the next building which is of a lower height than the first. If his speed is $9\mathrm{m}/s$, the (horizontal) distance between the two building is $10\mathrm{m}$ and the height difference is $9\mathrm{m},$ will he be able to land on the next building? (take $\mathrm{g}=10\mathrm{m}/{\mathrm{s}}^2$)

A ball is dropped from a building of height $45 \mathrm{m}$. Simultaneously another ball is thrown up with a speed $40 \mathrm{m}/\mathrm{s}$. Calculate the relative speed of the balls as a function of time.