When a driver brakes an automobile, the friction between the brake drums and the brake shoes converts the car's kinetic energy to thermal energy. if a 1500-kg automobile traveling at 35 m/s comes to a halt, how much does the temperature rise in each of the four 8.0 kg iron brake drums? (the specific heat of iron is 448 j/(kg · °

64.1°C

Explanation:

mass of automobile, M = 1500 kg

velocity, v = 35 m/s

mass of each brake, m = 8 kg

specific heat of iron, c = 448 J/kg°C

According to the conservation of energy

the kinetic energy of automobile = thermal energy of brakes

0.5 Mv² = 4 x m x c x ΔT

where, ΔT is the rise in temperature of the brake

0.5 x 1500 x 35 x 35 = 4 x 8 x 448 x ΔT

ΔT = 64.1°C

Thus, the change in temperature of each brake is 64.1°C.

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.