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An explosion blows a rock into three par...

An explosion blows a rock into three parts. Two parts go off at right angles to each other . These two are `1 kg` first part moving with a velocity of `12 ms^(-1) and 2 kg` second part moving with a velocity of `8 ms^(-1)`. If the third part flies off with a velocity of `4 ms^(-1)`. Its mass would be

A

5 kg

B

7 kg

C

17 kg

D

3 kg

Text Solution

Verified by Experts

The correct Answer is:
A
Law of conservation of momentum
`|(m_(1)v_(1))hat(i) + (m_(2)v_(2))hat(j)| = m_(3)v_(3)`
`rArr sqrt(P_(1)^(2) + P_(2)^(2)) = P_(3)`
`rArr m_(3) xx 4 = sqrt(12^(2) + (2 xx 8)^(2))`
`rArr m_(3) = (20)/(4) = 5kg `
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