Given two amsses, 3m and 4m, where the 3m mass is moving with a velocity v1 colliding with the 4m mass, which is suspended by a string of length L. The two masses are stuck together as the result of the collision. The compound system swings to the right and stops at the horizontal level. Find the kinetic energy K of the compound (theoretically).
2007-11-17 06:01:24 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Assuming you are supposed to solve this by conservation of energy, then the kinetic energy of 3m is transferred entirely to the compound when it comes to rest.
1/2 3m v1^2 = (3m+4m) g L
so the Ke of the compound at any point inbetween is Ke - Pe, where the Pe is a function of L sin?
2007-11-17 06:59:33 · answer #1 · answered by Piglet O 6 · 0⤊ 1⤋
there's an inelastic collision between 3m and 4m, the momentum is conserved.
3m * v1 = (3m + 4m) * v2
v2 = 3v1/7 is the initial velocity of the compound.
so
K = 1/2 * 7m * v2^2
= 1/2 * 7m * (3*v1/7)^2
= 7m/2 * 9/49 * v1^2
=9mv1^2/14
it should be equal to 7mgL.
2007-11-17 07:34:59 · answer #2 · answered by zsm28 5 · 0⤊ 0⤋