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

Explanation

From the law of conservation of momentum,
`p_(3)=sqrt(p_(1)^(2)+p_(2)^(2))`
`implies m_(3)xx4=sqrt((1xx12)^(2)+(2xx8)^(2))=20 implies m_(3)=5 kg`