C.V. Car. Car looses kinetic energy and brake system gains internal u.
No heat transfer (short time) and no work term.
m = constant; E2 - E1 = 0 - 0 = mcar 1/2(V22 − V21) + mbrake(u2 − u1)
The brake system mass is two different kinds so split it, also use Cv since we do not have a u table for steel or brake pad material.