A 1000 kg vehicle travelling at 80 m/s impacts a plunger attached to a piston-cylinder arrangement. If all of the energy of the vehicle is absorbed by the 20 kg of liquid contained in the cylinder, what is the maximum temperature rise of the liquid? (The specific heat of the liquid is 4.0 kJ/kg.°C)
- A. 55°C
- B. 40°C
- C. 45°C
- D. 50°C
Answer: B. 40°C
Explanation: Kinetic Energy $KE = 0.5 m v² = 0.5(1000)(80^2) = 3.2$ MJ. Heat $Q = mc\Delta T = 20(4.0)\Delta T = 80 \Delta T$ kJ. $3200 = 80 \Delta T \Rightarrow \Delta T = 40$.