Question

(a) Differentiate between average velocity and average speed.
(b) A car is moving along a straight line OP as shown below. It moves from 0 to P in 18 s and returns from P to Q in 6 s. What is the average velocity and the average speed of the car while going :
(i) from 0 to P and
(ii) from 0 to P and back to Q ?

CBSE Class IX Science LA (5 Marks)

Answer 1

(a) The average speed of an object is obtained by dividing the total distance travelled by the total time taken while average velocity is given by the arithmetic mean of initial velocity and final velocity for a given period of time. 

(b) (i) While going from 0 to P

Average velocity = Total displacement /Total time = 360/18 = 20 m/s                     

Average speed = Total distance/ Total time = 360/18 = 20 m/s                            

(ii) While going from 0 to P and back to Q

     Average velocity = Total displacement / Total time = 240/24                                           = 10m/s             

Average velocity = Total distance/Total time 

                          =  360 + 120/18 + 6 = 480 / 24                                                  =20 m/s