P1 - Energy Flashcards
What’s the law of conservation?
Energy is always conserved - it cannot be created or destroyed
Extra: (It can be turned into mass), it is measured in Joules (J)
Sound/vibrational energy is the same as _______ energy
Kinetic
Fuels, food & cells/batteries have _______ ________ energy
Chemical potential
What is kinetic energy?
Kinetic energy is the energy stored in moving objects
Do stationary objects have kinetic energy?
No
What is elastic potential energy?
Elastic potential energy is the energy stored in a stretched spring
What is gravitational potential energy?
Gravitational potential energy is the energy stored in an object due to its position above the Earth’s surface
Extra: This is due to the force of gravity acting on an object
What is specific heat capacity of a substance?
Specific heat capacity of a substance is the amount of energy required to raise the temperature of 1kg of the substance by 1 degree celsius
What is a system in physics?
A system is an object or a group of objects
What’s it called when no energy can enter or leave?
Closed system
Where does a pendulum have its maximum GPE of the mass?
The highest point of its swing
Where does a pendulum have its maximum KE of the mass?
At the lowest point of its swing
Why does a pendulum gradually come to a stop?
There’s friction on the fixed point and in the air particles which creates thermal energy. This is dissipated since it’s not needed
How can we reduce unwanted energy transfers in a pendulum?
By reducing friction
Extra:
- To do this use a lubricant e.g. oil (on the fixed point)
- Remove air particles around the pendulum
How is energy transferred for a bungee jumper?
Before a bungee jumper jumps, he has a store of gravitational potential energy
When the student’s falling, the store of kinetic energy increases
When the bungee rope is stretched, the rope stores energy as elastic potential energy
Why does the bungee jumper never return back to the original positon?
Because energy is dissipated as thermal energy
Extra - This is due to:
- Friction with air particles
- Stretching effects in the bungee rope
When is work done?
When energy is transferred from one store to another
What is power?
Power is the rate at which energy is transferred or the rate at which work is done
TRUE OR FALSE: 1 watt (W) is an energy transfer (or work done) of 1J per second
TRUE
What does efficiency tell us?
Efficiency tells u what fraction of the energy we put into an appliance is transferred to useful forms of energy
