Q.

A particle moving in a straight line covers half the distance with speed 6 m/s. The other half is covered in two equal time intervals with speeds 9 m/s and 15 m/s respectively. The average speed of the particle during the motion is              [2024]

1 8.8 m/s  
2 10 m/s  
3 9.2 m/s  
4 8 m/s  

Ans.

(4)

BCs=9t+15t=24t

ACs=6t1=24tt1=4t

vav=dist.time=48t2t+t1

vav=48t2t+4t48t6t8 m/s