A brick having a mass of 4.0 kg is dropped from a height of 2.0 m into a river that is 1.0 m deep. Assuming 80 % of the gravitational potential energy is ultimately transformed into thermal energy, determine this thermal energy in calories.

Step-by-step solution

Total height fallen by the brick is h = 2.0 + 1.0 = 3.0 m Loss in gravitational potential energy is U = mgh Taking g = 10 m/s ^2 , we get U = 4.0 10 3.0 = 120 J Thermal energy produced is 80 % of the loss in potential energy E = 0.80 120 = 96 J Converting joules to calories using 1 cal 4.2 J E = 96 4.2 22.85 cal The closest value among the options is 23 cal