A two stage rocket is fired vertically upward from rest with acceleration as shown in a-t graphs. After 15 sec, the first stage burns out and second stage ignites. Choose the INCORRECT statement regarding motion of rocket in the time interval `0letle40s`.

Options

A. at t=15 sec, the speed of rocket is 15.0m/s
B. At t=20 sec, the speed of rocket is 300m/s
C. In time interval t=0 sec to t=15 sec, the distance travelled by rocket is 750 m.
D. in time interval t-0 sec to t=20 sec, the distance travelled by rocket is 1500 m.

Answer

D

Explanation

`v{{:((2t^(2))/(9)hatj,"if "0letle15sec),(150+150(5-15)+15(t-15)^(2)hatj,"if "15sletle40s):}`
at t=15
`r=(2xx15xx15xx15)/(3xx3)=750m`