# NCERT Physics Class 11 Exemplar Ch 4 Motion in a Plane Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

Doorsteptutor material for NCO Class-11 is prepared by world's top subject experts: fully solved questions with step-by-step explanation- practice your way to success.

## 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 non-collinear, non-co-planar 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.