Q21 of 37 Page 23

A boy travelling in an open car moving on a levelled road with constant speed tosses a ball vertically up in the air and catches it back. Sketch the motion of the ball as observed by a boy standing on the footpath. Give explanation to support your diagram.

Let’s assume the boy throws the ball with vertical velocity uy and the velocity of the car is ux.


Therefore, the horizontal velocity of the ball is ux with respect to the boy on the footpath.


Hence, the motion with respect to the boy on the footpath is parabolic like that of a projectile


The resultant velocity of the ball is


Angle of projection



More from this chapter

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19

A football is kicked into the air vertically upwards. What is its

(a) Acceleration, and (b) velocity at the highest point?


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A, B and C are three non-collinear, non-co-planar vectors. What can you say about direction of A × (B × C)?

 22

A boy throws a ball in air at 60° to the horizontal along a road with a speed of 10 m/s (36km/h). Another boy sitting in a passing by car observes the ball. Sketch the motion of the ball as observed by the boy in the car, if car has a speed of (18km/h). Give explanation to support your diagram.

 23

In dealing with motion of projectile in air, we ignore effect of air resistance on motion. This gives trajectory as a parabola as you have studied. What would the trajectory look like if air resistance is included? Sketch such a trajectory and explain why you have drawn it that way.