THERMAL ENERGY
What is thermal energy?
The total energy of motion of the particles in a substance.
What does a thermometer measure?
Temperature.
What is kinetic energy?
The energy of motion.
What is the formula for kinetic energy?
KE = ½ mv²
What does the law of conservation of energy say?
Energy cannot be created or destroyed, only transformed.
What happens to thermal energy when an object is heated?
It increases.
What happens to particles in a substance as it gets hotter?
They move faster.
What is potential energy?
Stored energy due to position or condition.
What is the formula for potential energy?
PE = mgh
When you drop a ball, what energy transformation happens?
Potential energy → kinetic energy.
Which has more thermal energy: a lake at 20°C or a cup of water at 90°C?
The lake (because it has more particles, even though it's cooler).
Which has a higher temperature: boiling water or melting ice?
Boiling water.
Give an example of an object with potential energy.
A stretched rubber band or a book on a shelf.
A ball (2 kg) moves at 3 m/s. What is its kinetic energy?
KE = ½ × 2 × 3² = 9 J
True or False: A moving car has both kinetic and potential energy.
True.
What’s the relationship between thermal energy and particle movement?
The faster the particles move, the more thermal energy there is.
What is the difference between heat and temperature?
Temperature measures average particle motion; heat is energy transfer.
What factors affect kinetic energy?
Mass and speed.
A box (5 kg) is on a shelf 2 m high. What is its potential energy? (g = 9.8)
PE = 5 × 9.8 × 2 = 98 J
When energy changes form, do we lose it?
No, it transforms or transfers, but total energy stays the same.
True or False: Thermal energy depends only on temperature.
False (it also depends on mass and number of particles).
If two objects reach the same temperature, what is this called?
Thermal equilibrium.
At what point does a roller coaster have the most potential energy?
At the highest point.
A car (1,000 kg) moves at 20 m/s. What is its kinetic energy?
KE = ½ × 1000 × 400 = 200,000 J
What happens to mechanical energy in a closed system with friction?
Some is transformed into thermal energy.