A trolley is moving away from a stop with an acceleration `a=0.2 m//s^(2)`. After reaching the velocity u=36 km/h, it moves with a constant velocity for the time of 2 min. then, it uniformly slows down, and stops after further travelling a distance of 100 m. find the average speed all the way between stops.

Options

A. `76/17 m//s`
B. `208/21 m//s`
C. `85/12 m//s`
D. `155/19 m//s`

Answer

D

Explanation

`v=36xx5/18=10 m//s`
v=at
10=0.2 x t
t=50
`1/2 xx txx10=100`
t=20 sec.
dist. `=1/2 xx(190+120)xx10 =1550m`
`v_(av)=1550/190 =155/19 m//s`