If the displacement$-$time graph for a particle is parallel to time axis, what is the velocity of the particle ?

What kind of motion of a body is represented by the graphs given below ?

The numerical ratio of displacement to distance for a moving object is

The average time taken by a normal person to react to an emergency is one$-$fifteenth of a second and is called the 'reaction time'. If a bus is moving with a velocity of $60\, km h^{-1}$ and its driver sees a child running across the road, how much distance would. the bus had moved before he could press the brakes ? The reaction time of the people increases when they are intoxicated. How much distance had the bus moved if the reaction time of the driver were $\frac{1}{2}\, s$ under the influence of alcohol ?

Give examples to distinguish

$(i)$ Distance and displacement.

$(ii)$ Speed and velocity.

$(iii)$ Acceleration and retardation.

Answer the following questions

$(i)$ State the type of motion shown by a freely falling stone.

$(ii)$ When a stone is thrown vertically upwards its velocity is continuously decreased. Why ?

$(iii)$ Give an example of a motion in which average velocity is zero, but the average speed is not zero.