Thermal Energy
Define thermal energy.
Energy due to particle motion
What is the Law of Conservation of Energy?
Energy cannot be created or destroyed.
What is work?
Energy transfer due to force causing displacement.
What is power?
The rate of doing work or transferring energy.
What is an example of conduction?
Heat from a stove to a pot.
Name 3 ways thermal energy transfers.
Conduction, convection, and radiation.
What is the formula for kinetic energy?
Ek=1/2 x m x v2
What is the formula for work?
W = F x d
What is the formula for power?
What kind of energy do you have when you are at the very top of a roller coaster before you go down?
potential energy
Example of radiation?
Heat from the Sun or a campfire.
Explain potential and kinetic energy in a falling object.
Potential decreases as height lowers, while kinetic increases. Total energy remains constant.
What are the units for work?
What are the units for power?
Watts (W)
What is an example of convection?
the AC turning on and makes the air in the room colder
Conduction vs. convection?
Conduction transfers heat via direct contact; convection uses fluid motion.
What happens to energy during friction?
Mechanical energy transforms into thermal energy.
A 10 N force moves an object 5 m. How much work is done?
W = 5 x 10 = 50 J
100 J of work is done in 5 seconds. What is the power?
P = 100 / 5 = 20 W
Why do ice cubes melt faster on metal surfaces compared to wood?
Metal conducts heat better than wood, transferring thermal energy to the ice faster.
Role of insulation in heat transfer?
Insulation slows conduction to prevent heat loss.
A 5 kg object is dropped from a height of 10 m. Assuming no air resistance, how much kinetic energy does it have just before hitting the ground (aka max kinetic energy?
The total mechanical energy is conserved, so the potential energy at the top becomes kinetic energy at the bottom:
Eg = mgh = 5 x 9.8 x 10= 490 J
Therefore, the kinetic energy just before hitting the ground is 490 J
If a machine is putting in 453 J of work and is displaced 12 m, how much force was used?
37.75 N
Why is power important in machines?
It indicates how efficiently work can be done over time, like lifting heavier loads faster.
A cyclist moving downhill applies brakes, which slow the bike by converting some kinetic energy into thermal energy. Where does the thermal energy go?
It dissipates into the surroundings as heat, warming the brake pads and air.