Amount of Kinetic Energy Lost in Inelastic Collision

[addy899]

1. Two carts, each of mass M, travel towards each other on a frictionless air track, one with velocity V, and the other with -3V. They collide and stick together. How much kinetic energy is lost in the collision?

2. P = mv, KE=1/2mv²

3. Initial KE of the system is the sum of the kinetic energies of the two masses.

K1 = (1/2)Mv², K2 = (1/2)m(-3v)² = 9mv²

sum: 10mv²

assuming momentum is conserved, velocity of the two masses after the collision is -V.

Then calculate final KE = 1/2(2m)(-V)² = mv²

subtract this from the initial and I get 9mv² Joules are lost in the collision.

My key says the answer is 4mv²

 

[barryj]

K1 = (1/2)Mv2, K2 = (1/2)m(-3v)2 = 9mv2

sum: 10mv2

check your arithmetic.

 

[addy899]

forgot to divide by 2... goodness. Thanks!