NCERT Physics Class 11 Exemplar Ch 4 Motion in A Plane Part 3
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VSA
16 A cyclist starts from centre O of a circular park of radius 1km and moves along the path OPRQO as shown. If he maintains constant speed of, what is his acceleration at point R in magnitude and direction?
Ans: 16.
in the direction RO.
17 A particle is projected in air at some angle to the horizontal, moves along parabola as shown in Fig. 4, where x and y indicate horizontal and vertical directions, respectively. Show in the diagram, direction of velocity and acceleration at points A, B and C.
Ans:
The students may discuss with their teachers and find answer.
18 A ball is thrown from a roof top at an angle of 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.
(c) Greatest acceleration? Explain
Ans:
(a) Just before it hits the ground.
(b) At the highest point reached.
(c) constant.
19 A football is kicked into the air vertically upwards. What is its (a) acceleration, and (b) velocity at the highest point?
Ans:

Acceleration.

Velocity.
20 A, B and C are three noncollinear, noncoplanar vectors. What can you say about direction of?
Ans:
Since is perpendicular to plane of B and C, cross product of any vector will lie in the plane of B and C.