Practice Thermal Energy in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

The total kinetic energy of all particles in an object due to their random motion.

The energy of jiggling atoms and molecules—what we experience as temperature.

Example 1

easy
How much thermal energy is needed to heat 2 \text{ kg} of water from 20°\text{C} to 80°\text{C}? The specific heat capacity of water is c = 4186 \text{ J/(kg·°C)}.

Example 2

medium
A 0.5 \text{ kg} iron block (c = 450 \text{ J/(kg·°C)}) at 200°\text{C} is dropped into 2 \text{ kg} of water (c = 4186 \text{ J/(kg·°C)}) at 20°\text{C}. What is the final equilibrium temperature?

Example 3

medium
A 3 \text{ kg} aluminum block (c = 900 \text{ J/(kg·°C)}) absorbs 54{,}000 \text{ J} of thermal energy. What is the temperature increase?

Example 4

hard
A 1200 \text{ kg} car traveling at 30 \text{ m/s} brakes to a stop. If all kinetic energy is converted to thermal energy in the brakes (4 \text{ kg} of steel, c = 500 \text{ J/(kg·°C)}), by how much do the brakes heat up?
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