Q20 of 37 Page 22

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

Let the cross product of



Therefore, K vector will be perpendicular to both B and C.


And when we will take cross product of K with A



It will be perpendicular to both K and A. Therefore, M will lie on a plane containing vector B and C


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A ball is thrown from a roof top at an angle of 45° above the horizontal. It hits the ground a few seconds later. At what point during its motion, does the ball have

(a) Greatest speed.


(b) Smallest speed.


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

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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.

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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.