Homework Help: physics

Posted by tina on Wednesday, February 25, 2009 at 11:23pm.

two different masses have equal, non zero kinetic energies. the momentum of the smaller mass is?

what is the magnitude of momentum of a 0.140 baseball traveling at 45.0m/s?

a 2.00g bullet hits and becomes embedded in 5.00 kg wood block which is hanging from a 1.60m long string. this causes the block to swing through an arc of 5.50(degrees). what was the speed of the bulletbefore it hit the block ?

a 14000kg boxcar is coasting at 1.50m/d along a horizontal track when it hits and couples with a stationary 10000kg boxcar. what is the speed of the cars after the collision?

physics - drwls, Thursday, February 26, 2009 at 2:16am
Let m be the smaller mass and v be the velocity of that mass. Let M be the larger mass and V be its velocity.

Because the energies are equal,
m v^2 = M V^2
(mv)^2/m = (MV)^2/M

mv/(MV) = sqrt (m/M) < 1
(since m/M < 1)

Therefore the smaller mass also has less momentum.
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You left out the dimensions of the mass of the baseball. I assume it is kg

Momentum magnitude is mass x velocity. You should know that. Do the calculation. Don't forget the units, which should be kg m/s

Your last two questions require you to apply the law of conservation of momentum

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