Legend

 p = momentum m = mass v = velocity Fav = average force t = time Vi = initial velocity Vf = final velocity

¤½¦¡

 Type Conservation of momentum equation Conservation of energy equation Elastic: Colliding objects are so hard that no momentum or energy is lost (such as through shock absorption or the objects sticking together for any length of time) p of objects 1 & 2 before = p of objects 1 & 2 after X component: m1v1ix + m2v2ix = m1v1fx + m2v2fx Y component: m1v1iy + m2v2iy = m1v1fy + m2v2fy KE of objects 1 & 2 before = KE of objects 1 & 2 after 1/2m1v1i2+1/2m2v2i2 = 1/2m1v1f2+ 1/2m2v2f2 Since KE is scalar, don't need to consider x and y components Inelastic: Colliding objects are not completely hard, so some energy is lost when objects deform during collision, and objects are in contact for some time. p of objects 1 & 2 before = p of objects 1 & 2 after KE is not conserved, but the total energy is. Completly inelastic: Colliding objects remain stuck together after impact. p of objects 1 & 2 before = p of objects 1 & 2 after m1v1 + m2v2 = (m1 + m2)vf KE is not conserved, but the total energy is. KE of objects 1 & 2 before = KE of objects 1 & 2 after + any energy lost during impact. 1/2m1v1i2+1/2m2v2i2 = 1/2(m1 + m2)vf2 + any energy lost during impact.
 Interactive Lab Problems