A particle moving in a straight line covers half the distance with speed of 3 m/s.The other half of the distance is covered in two equal time intervals and with speeds of 4.5 m/s and 7.5 m/s,respectively. The average speed of particle during this motion is

Options

(a) 4 m/s
(b) 5 m/s
(c) 5.5 m/s
(d) 4.8 m/s

Correct Answer:

4 m/s

Explanation:

Average Speed for second half= 4.5+7.5/2 =6 m/s

If particle travels in two equal time interval, Average Speed  = 2v1*v2 / (v1+v2)

here v1=3 m/s and v2=6 m/s, so

Average Speed= 2*v₁*v₂/v₁+v₂ = 2*3*6 / (6+3) =36/9=4.0 m/s