P1 Energy and Dissipation Flashcards
What is the equation linking kinetic energy, mass and velocity?
Energy = 1/2 x mass x velocity^2
How do you find graviational potential energy?
Gravitational potential energy = weight x change in height
What is the scientific unit for graviational field strength?
Newtons per kilogram
What is the equation linking power, time and energy?
Power = energy/time
Which energy store changes as height of an object changes?
Graviational Potential Energy
Which two energy stores changes depending on the position of the object?
Gravitational Potential Energy
&
Elastic Potential Energy
For something that is falling, what is the relationship between Kinetic Energy and Gravitational Potential Energy?
Inverse proportion; as Kinetic energy increases, Gravitational energy decreases
Which type of energy is stored in an inflated balloon?
Elastic Potential Energy
What is the Law of Conservation of Energy?
Energy is stored and transferred.
- not created or destroyed
What is energy?
Energy is the ability to do work.
What are the energy stores?
1) Kinetic
2) Chemical
3) Gravitational
4) Elastic
5) Thermal
6) Magnetic
7) Nuclear
What is kinetic energy?
Energy in a moving object
What is chemical energy
Energy in a fuel or battery
What is graviational energy?
Energy in an object above the ground
What is elastic energy?
Energy in a streched or squashed object.
What is thermal energy?
Energy due to a substance’s temperature.
What is magentic energy?
Energy in 2 seperated magnets (attract/repel)
What is nuclear energy?
Energy in radioactive decay.
What are the energy transfers?
- Waves
- Heating
- ‘Electrical current’
- Mechanical
What is a closed system?
A system in which no energy transfers take place out of or into the energy stores of the system.
Energy transferred is equal to
Work done
How do you calculate work done?
Work done = force x distance
(J) (N) (m)
How to find change in graviational potential energy?
Change in graviational potential energy = weight x change in height
How to calclate weight?
Weight = Mass x Gravaitional field Strength (9.8N/Kg)
How to find elastic potential energy?
Elastic potential energy = 1/2 x spring constant x extention^2
What is useful energy?
Energy in the place and form we want it in.
What is wasted energy?
Energy that is not useful and is transferred by an undesired pathway.
What happens to wasted energy?
It is eventually transferred into the surroundings, which become warmer.
How to calculate efficiency?
Efficiency = useful output energy transfer / total input energy transfer
or
Efficiency = useful power output / total power input
How do you calculate work done?
Work done = force x distance
What does kinetic energy depend on?
Its mass and speed.
How do machines waste energy?
- Friction between moving parts
- Air resistance
- Electrical resistance
- Noise
Give an example on how we can reduce the amount of energy wasted in machines?
Lubrication to reduce friction between moving parts.
What is power?
The rate of transfer of energy.
What is power measured in?
Watts (W)
