Answer:
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