Two putty balls of equal mass moving with equal velocity in mutually perpendicular direction, stick together after collision. If the balls were initially moving with a velocity of `45sqrt(2)jms^(-1)` each, the velocity of their combined mass after collision is

Options

A. `45 sqrt(2)ms^(-1)`
B. `45ms^(-1)`
C. `90ms^(-1)`
D. `22.5 sqrt(2)ms^(-1)`

Answer

B

Explanation

Initial momentum `vec(P)= m 45 sqrt2 hat(i) + m 45 sqrt2 hat(j) rArr |vec(P)| = m xx 90`
Final momentum `2m xx V`
By conservation of momentum `2m xx V= m xx 90`
`therefore V= 45m//s`