A slingshot first shoots a rock, and then a steel ball with twicethe mass of the

Question

A slingshot first shoots a rock, and then a steel ball with twicethe mass of the rock. The force exerted by the slingshot in each case is the same and isexerted over the same distance. What can we say about the momentumand kinetic energy of the rock and the ball when they leave theslingshot?

A) They have the same momentum and the same kinetic energy.

B) The ball has a greater momentum and a greater kineticenergy.

C) The ball has a greater momentum, but they have the same kineticenergy.

D) They have the same momentum, but the rock has a greater kineticenergy. E) The rock has a greater momentum, but they have the same kineticenergy.

Explanation / Answer

B) The ball has a greater momentum and a greater kineticenergy.

So rock = mass m    Momentum:p=mv       KE=1/2mv2

steel ball = mass 2m     Momentum: p=2mv    KE = 1/2(2m)v2= mv2

Therefore we can say that: the ball has a greater momentum anda greater kinetic energy.

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