Question

1. wha causes the formation of heat when two metals rub together?

a. ozone
b. radiation
c. fraction
d. friction

1. robert brown examined the motion of:

a. protons
b. particles
c. popcorn
d. positrons

1. what kind of energy is the energy of motion?

a. potential energy
b. mechanical energy
c. nuclear energy
d. kinetic energy

1. it which direction does heat flow?

a. cold to hot
b. hot to cold
c. up
d. north to south

1. choose the best definition for temperature.

a. average kinetic energy
b. average potential energy
c. electromagnetic energy
d. total kinetic energy

Explanation:

1. When two metals rub together, the force of friction between them converts mechanical energy into heat energy. Ozone is a gas, radiation is a form of energy transfer (like light), and fraction is a mathematical term (e.g., \( \frac{1}{2} \)).
2. Robert Brown observed the random motion of particles (now known as Brownian motion). Protons are sub - atomic particles in the nucleus, popcorn is a food item, and positrons are anti - particles of electrons.
3. Kinetic energy is defined as the energy of motion. Potential energy is stored energy (e.g., due to height), mechanical energy is the sum of kinetic and potential energy, and nuclear energy is energy stored in the nucleus of an atom.
4. Heat always flows from a region of higher temperature (hot) to a region of lower temperature (cold) according to the second law of thermodynamics.
5. Temperature is a measure of the average kinetic energy of the particles in a substance. Potential energy is not related to temperature in this context, electromagnetic energy is a different form of energy (like light), and total kinetic energy would depend on the amount of substance (not just temperature).

Answer:

1. D. friction
2. B. particles
3. D. kinetic energy
4. B. hot to cold
5. A. average kinetic energy