A1200 kg car traveling at 60 mph quickly brakes to a halt. the kinetic energy of the car is converted to thermal energy of the disk brakes. the brake disks (one per wheel) are iron disks with a mass of 4.0 kg. what is the increase in temperature of the brakes?

 ΔT = 59.9 ° C

Explanation:

For this exercise the brake energy is totally converted into heat

Let's calculate the vehicle energy

       K = ½ m v²

Let's reduce the units to the SI system

       v = 30 mph (1609.34 m / mile) (1h / 3600s) = 13.41 m / s

      Em = K = ½ 1200 13.41²

      K = 1.079 105 J

All this energy is transformed into heat

     Em = Q

The expression for heat is

     Q = m   ΔT

     ΔT = Q / m

The specific heat of iron is = 450 J / Kg ºC

     ΔT = 1,079 105 / (4.0 450)

     ΔT = 59.9 ° C

we need answer choices

0.11 m/s and 0.28 m/s should be correct