A 120 kg mass is blown apart into a 80 kg piece and a 40 kg piece.After the blast,the two masses are moving apart with a relative velocity of 60 m/s.The velocity of the 80 kg mass is
A) 59 m/s.
B) 51 m/s.
C) 34 m/s.
D) 20 m/s.
E) 14 m/s.

Question

Quizplus · Accepted Answer

We can use conservation of momentum to solve this problem. The initial momentum of the system before the explosion is zero, since the object was at rest. Therefore, the total momentum after the explosion must also be zero.

We can write the equation for conservation of momentum as:

m1v1 + m2v2 = 0

where m1 and v1 are the mass and velocity of the 80 kg piece, and m2 and v2 are the mass and velocity of the 40 kg piece.

Since the two pieces are moving apart with a relative velocity of 60 m/s, we know that:

v1 - v2 = 60

Solving these two equations for v1, we get:

v1 = (m2/m1 + m2) * 60

Plugging in the values for m1 and m2, we get:

v1 = (40/80 + 40) * 60 = 20 m/s

Therefore, the velocity of the 80 kg mass is 20 m/s, which corresponds to choice D.

A 120 Kg Mass Is Blown Apart into a 80