I am trying to find the "mass" of an object of an inelastic collision.

Question

Here is the information that I have. Vinny is wearing a suit made of Velcro (the soft fuzzy side). Starting from rest, "velcro vinny" runs along level ground accelerating at 7.6m/s2 for 3 seconds. At exactly 3 seconds, he collides with a stationary crate full of ninjas (m= 12.3 (209.10) kg). This crate is conveniently covered in the hard prickly side on Vinny's suit. Vinny and the CFON stick together and slide along the same level ground (mk=0.5) coming to rest 35 meters from Vinny's original starting point. What is Velcro Vinny's mass? PLEASE HELP!

Answer 1

Sounds like a classic case of pure inelastic collision:

http://en.wikipedia.org/wiki/Inelastic_c...

Conservation of momentum is maintained so:

Mv Vv + Mc Vc = Mv Uv + Mc Uc

but:

Vc = the initial velocity of the crate = 0, and

Uv = final velocity of Vinny and Uc = final velocity of the crate are equal, so

Mv Vv = Ub(Mv + Mc)

We can find Vv because Vinnie's initial acceleration was constant, and the formulas for motion under constant acceleration are:

Vf = Vi + A T

D = Vi T + (1/2) A T^2

where T is the time interval

A is the acceleration

Vi is the initial velocity

Vf is the final velocity

For Vinnie, before he hit the crate, we know A, T, and Vi so we can determine Vf.

After the collision, Vinnie and the crate slow down together.

If mk is supposed to be the coefficient of friction, then this gives us the acceleration value (g/2 - where g is the gravitational acceleration, about 9.8 m/s^2). With the acceleration value and the distance, we can determine the time and the initial velocity.

So we have Vv and Ub, and Mc. Therefore we can solve:

Mv Vv = Ub(Mv + Mc)

for Mv.