Question

A car travels half the distance with constant velocity 50 km/h and other half with a constant velocity of 40 km/h, along a straight line. The velocity if the car in km/h is:

• A. 45
• B. 44.4
• C. 0
• D. $\sqrt{(50\times 40)}$

Answer 1

Answer: (B)

44.4

Let total distance$=2s$

during first half : $speed=50$ , $distancecovered=s$

during second half : $speed=40$ , $distancecovered=s$

$Averagevelocity=\frac{Totaldisplacement}{totaltimetaken}$

$<v>=\frac{s+s}{\frac{s}{40}+\frac{s}{50}}$

$<v>=\frac{2\times 40\times 50}{50+40}$

$<v>=44.4$