Question

A wagon full of medicine balls is rolling along a street. Suddenly one medicine ball (3 kg) falls off the wagon. What happens to the speed of the wagon?

A wagon full of medicine balls is rolling along a street. Suddenly one medicine ball (3 ) falls off the wagon. What happens to the speed of the wagon?

The wagon speeds up, because the mass of the wagon decreased, but the momentum must be constant

The wagon slows down, because the mass and therefore the momentum of the wagon decreased.

The speed of the wagon does not change, because no external force is exerted on the wagon.

Additional information about the ball's motion is needed to answer.

Answer 1

If the one medicine box falls, then after that momentum of van must remains constant, So

Using momentum conservation:

Pi = Pf

M*V = m1*v1 + m2*v2

M = Initial mass of wagon with all the medicine ball

m1 = mass of one medicine ball

m2 = mass of wagon and remaining medicine balls

v1 = speed of one medicine ball after it falls of = 0 m/sec

v2 = speed of remaining wagon = ?

So,

M*V = m1*0 + m2*v2

v2 = M*V/m2

v2 = (M/m2)*V

since M/m2 > 1, So v2 > V

Which means wagon will speeds up, because the mass of the wagon decreased, but the momentum must be constant.

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