An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass 1 kg moves with a speed of 12 ms^(-1)and the second part of mass 2 kg moves with 8 ms^(-1)speed. If the third part flies off with 4 ms^(-1)speed, then its mass i s .....

An explosion breaks a rock into three parts in a horizontal plane. Two

1.	An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass 1 kg moves with a speed of 12 ms^(-1)and the second part of mass 2 kg moves with 8 ms^(-1)speed. If the third part flies off with 4 ms^(-1)speed, then its mass i s .....
Answer» 17 kg 3 kg 5 kg 7 kg Solution : Supposemass of rockis M andvelocity`vec( V )= 0 ` massof firstpiece`m_(1) = 1` kgandvelocity`vec( v) _(1) = 12 hat(I ) m//s` Mass of thirpiece`m_(3)=?`andmagnitude ofvelocity`v_(3) =4 m//s` From the lawof conservationof momentum Momentum ofrock= addition of momentum Magnitude`m_(3) v_(3) = SQRT((12)^(2) + (16)^(2))` `=sqrt(144+256)` `=sqrt(400) =20 KGMS^(-1)` `m_(3)= (20)/(v_(3) ) = (20)/(4) =5 kg`