what has more momentum, a baseball traveling at 4 m/s or a baseball traveling at 16m/s ? and which has more energy ?

(1) Answers

We know the formulas for momentum and energy. But they both involve the mass of the object, and we don't know the mass of the baseball.  What can we do ? It's not a catastrophe.  The question only asks which one is bigger.  If we're clever, we can answer that without ever knowing how much the momentum or the energy actually is.  We know that both baseballs have the same mass, so let's just call it ' M ' and not worry about what it really is. Momentum of anything = (mass) x (speed) Momentum of the first baseball = (M) x (4 m/s) = 4M Momentum of the second one = (M) x (16 m/s) = 16M The second baseball has 4 times as much momentum as the first one has. Kinetic energy of anything = 1/2 (mass) x (speed squared) KE of the first baseball = 1/2 (M) x (4 squared) = 8M KE of the second one = 1/2 (M) x (16 squared) = 128M The second baseball has 16 times as much kinetic energy as the first one has.

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