Question

14. A racing car accelerates uniformly through three gears, changes with the following average speed:

20 for 2.0 s
40 for 2.0 s
60 for 6.0 s

What is the overall average speed of the car?

A. 12
B. 13.3
C. 40
D. 48
E. 37

Answer 1

s=s1+s2+s3 =20•2+40•2+60•6 =480 m
t=t1+t2+t3 =2+2+6 =10s
v(ave) =s/t =480/10=48 m/s
---D