## An artificial satellite is moving in a circular orbit of radius

[question] Question. An artificial satellite is moving in a circular orbit of radius 42250 km. Calculate its speed if it takes 24 hours to revolve around the earth. [/question] [solution] Solution: Distance covered by the satellite in 24 hours. $S=2 \pi r$ $=2 \times \frac{22}{7} \times 42250$ $=265571.43 \mathrm{~km}$ Therefore speed of satellite $v=\frac{\text { distance travelled }}{\text { time taken }}=\frac{265571.43}{24 \times 60 \times 60}=3.07 \mathrm{kms}^{-1}$ [solution]...

## State which of the following situations

[question] Question. State which of the following situations are possible and give an example for each of these: (a) An object with a constant acceleration but with zero velocity. (b) An object moving in a certain direction with acceleration in the perpendicular direction. [/question] [solution] Solution: (a)A body with a constant acceleration but with zero velocity is possible. For example, when a body is just released, its initial velocity u = 0, but acceleration g = 10 ms–2 (b)It is possible ...

## The speed-time graph for a car is shown in figure below.

[question] Question. The speed-time graph for a car is shown in figure below. (a) Shade the area on the graph that represents the distance travelled by the car during the first 4 seconds. (b) Which part of the graph represents uniform motion of the car ? [/question] [solution] Solution: (a)During first 4 seconds, car is moving with non-uniform acceleration. Area of shaded portion represents distance travelled. (b)The straight line portion of the graph represents uniform motion of the car. [/solu...

## An athlete completes one round of a circular track of diameter 200 m in 40 s.

[question] Question. An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s ? [/question] [solution] Solution: Given Diameter of circular track, $2 \mathrm{r}=200 \mathrm{~m}$ Circumference of circular track $=2 \pi \mathrm{r}$ $s=\pi(2 r)=\frac{22}{7} \times 200=\frac{4400}{7} \mathrm{~m}$ Time for completing one round $=40 \mathrm{~s}$. Time for which the athlete ran $=2 \mathrm{~min}$ an...

## When will you say a body is in

[question] Question. When will you say a body is in (i) Uniform acceleration ? (ii) Non uniform acceleration ? [question] [solution] Solution: (i) A body is in uniform acceleration when it moves in a straight line and equal changes of velocity take place in equal intervals of time. (ii) A body is said to be possessing non-uniform acceleration when unequal changes in velocity take place in equal intervals of time....

## An object has moved through a distance. Can it have zero displacement?

[question] Question. An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example. [/question] [solution] Solution: Yes, an object which has moved through a distance can have zero displacement. Example : When a person, walking along a circular path, returns back to the starting point, after completing a circle, his displacement is zero. But he covers a distance 2r, where 'r' is the radius of circular path. [/solution]...