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-,its mass would be from Physics Laws of Motion Class 11 Manipur Board
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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-,its mass would be

  • 5 kg 

  • 7 kg

  • 17 kg

  • 3 kg


A.

5 kg 

apply the law of conservation of linear momentum. 

momentum of first part = 1 x 12 = 12 kg ms-1
Momentum of the second part  = 2 x 8 = 16 kg ms-1 '

Resultant monmentum

= [(12)2 +(16)2]1/2 = 20 kg ms-1

The third part should also have the same momentum.


Let the mass of third part be M, then 

4 x M = 20

M = 5 kg

apply the law of conservation of linear momentum. 

momentum of first part = 1 x 12 = 12 kg ms-1
Momentum of the second part  = 2 x 8 = 16 kg ms-1 '

Resultant monmentum

= [(12)2 +(16)2]1/2 = 20 kg ms-1

The third part should also have the same momentum.


Let the mass of third part be M, then 

4 x M = 20

M = 5 kg
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