Question

(a) Define circular motion.
(b) What is the difference between uniform motion in a straight line and circular motion ?
(c) An athlete completes one round of a circular track of diameter 200 m in 40 sec. What will be the distance covered and the displacement at the end of 2 min and 20 sec ?

CBSE Class IX Science LA (5 Marks)

Answer 1

(i) The motion of the body moving around a fixed point in a circular path is called circular motion.

S.No.              Uniform motion in straight line            Uniform circular motion 1.            The direction of motion of object          Direction changes                   does not change.                                continuously. 

 2.           If an object moves with a  

               constant speed.

             Its acceleration is zero.                       Acceleration is not zero.

(iii)          Diameter of track = 200 m

                   Radius = 100 m

The distance covered in 40 sec = 2tr = 2t 100

                                           = 2007c

= 200'/40 x100 = 15.7 m/s

The distance covered in 2 min 20 sec = 140 sec

                                           = 15.7 x 140 s

                                           = 2200 m

Number of complete rounds covered by athlete = 2000 /200n 

                                     = (2200 x 7)  = (200 x 22)

 = 3 1/2

He covers 3 1/2 rounds.