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 m/s and the second part of mass 2 kg moves with 8 m/s speed. If the third part flies off with 4 m/s speed, then its mass is??

yes, I am agree with dhreej.

  • -31

Of 1kg mass mv= 1*12=12

of 2kg mass mv=2*8=16

they go off at right angles.

their resultant will be under root( 122+162)= under root(400)

= 20

the third body moves in opp direction to this resultant

according to law of conservation of momentum

mv=20

m*4=20

m=5kg

  • 129
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