A particle moves in straight line in same direction for 20 seconds with velocity `3 m//s` and the moves with velocity `4 m//s` for another 20 sec and finally moves with velocity `5 m//s` for next 20 seconds. What is the average velocity of the particle?

Answer

D

Explanation

Let acceleration of B `vec(a)_(B)=a_(B) hat(i)`
Then acceleration of A w.r.t.
`B=vec(a)_(A)-vec(a)_(R)=(15-a_(B))hat(i)+15 hat(j)`
This acceleration must be along the inclined pplane
so `tan 37^(@)=15/(15-a_(B))rArr 3/4=15/(15-a_(B)) a_(B)=-5`
`rArr vec(a)_(R)=-5hat(i)`