Three particles of masses `20g`, `30g` and `40g` are initially moving along the positive direction of the three coordinate axes respectively with the same velocity of `20cm//s`. When due to their mutual interaction, the first particle comes to rest, the second acquires a velocity `(10hati+20hatk)cm//s`. What is then the velocity of the third particle?

Options

A. `2hati+3hatj+4hatk`
B. `2.5hati+15hatj+5hatk`
C. `2.5hati+10hatj-5hatk`
D. `2hati-3hatj-4hatk`

Answer

B

Explanation

`P_(1)=20xx20hati, P_(3)=40xx20hatk`
`P_(2)=30xx20 hatj`
`P_(1)=P_(1)+P_(2)+P_(3)=P_(f)`
`rArr 400i+600hatj+800hatk=30(10i+20 hatk)+40 v`
get `V=(100i+600hatj+200hatk)/40`
`=2.5 hati+15 hatj +5 hatk`