Energy up to level 6 Flashcards
State the 10 different stores of energy
Magnetic potential energy
Kinetic energy
Thermal energy
Light energy
Gravitational potential energy
Chemical potential energy
Sound energy
Elastic potential energy
Electric potential energy
Nuclear potential energy
What are the energy transfers for a torch
Chemical potential energy –> Electric potential energy –> Light energy
What are the energy transfers for a falling ball?
Gravitational potential energy –> Kinetic energy –> Sound and thermal energy
What is the law of conservation of energy?
Energy cannot be created or destroyed, it can only be transferred from one store to another
A car with an energy input of 500,000J from chemical potential energy transfers 350,000J into kinetic energy and 25,000J into light energy. Explain how you would calculate the energy it transfers into the thermal energy store.
The law of conservation of energy states that the total energy at the start and end of the process is the same.
This means that the total energy output must be 500,000J, becuase the total energy input is 500,000J. This means thermal energy is 500,000 - 350,000 - 25,000 = 125,000J
How do you calculate the energy transferred by a force?
Force transfer energy when they act over a distance. The formula relating force and distance is:
Work done (J) = Force (N) x distance (m)
‘Work done’ is the scientic way of saying ‘energy transferred’
Explain how energy is transferred when you apply the breaks on a car
When you apply the breaks on a car a force acts over a distance. This means that energy is transferred.
The transfers of energy are from the kinetic energy store (the car slows down) into the thermal energy store (the breaks get hotter)
What does the term ‘energy dissipation’ mean?
How does it happen?
Energy dissipation means that energy is transferred into stores where humans cannot make use of it.
The most common form of energy dissipation is when the energy is transferred into thermal energy in the environment. When this occurs the energy becomes ‘spread out’ and we are unable to access it.
What are the energy transfers in a bungee cord?
Gravitational potential energy –> kinetic energy –> elastic potential energy –> kinetic energy –> Gravitational potential energy
Why is it possible that humans might ‘run out’ of energy even though it cannot be created or destroyed
When we transfer energy, some of it is dissipated into thermal energy in the environment, where we cannot access it. The energy is still present but we are unable to make use of it, so we could run out of the energy that we are able to use.
What is the unit of energy?
The Joule (J)
How would you calculate the distance that you would have to push an object with a force of 15N to transfer a force of 90N?
The equation for work done can be placed in an equation triangle to help rearrange it.
Coving up distance gives work ÷ force = 90 ÷ 15 = 6m
State the equation to calculate gravitational potential energy.
What are the units that each part of the equation is measured in?
Gravitational potential energy = mass x acceleration due to gravity x height
GPE = m x g x h
Gravitaitonal potential energy is measured in Joules (J)
Mass is measured in kilograms (kg)
Acceleration due to gravity is measured in meters per second squared (m/s2)
Height is measured in meters(m)
Explain why lifting an object up 10m on Jupiter stores more gravitational potential energy than lifting the same object up 10m on Earth
this is becuase Jupiter has a stronger gravitational field strenght than Earth. This means it has a stronger acceleration due to gravity (g).
As gravitational potential energy = m x g x h. If g is larger then gravitational potential energy is also larger.
How do you calculate the amount of energy stored in the kinetic energy store of an object.
Example calculation: what is the kinetic energy store of an object that is moving at 5 m/s and has a mass of 10kg.
The kinetic energy store of an object can be calculated from this equation
Kinetic energy= 1/2 x mass x velocity squared
KE = 1/2 x m x v2
Mass is measured in kilograms (kg)
velocity is measured in meters per second (m/s)
Kinetice energy is measured in joules (J)
Example = 1/2 x 10 x 52
= 125J
How do you calculate the energy in the elastic potential energy store of a spring?
Example: What is the elastic potential energy stored in a spring with a spring constant of 4 N/m which is extended by 2m?
The elastic potential energy of a spring can be found by
elastic potential energy = 1/2 x spring constant x extension squared
EPE = 1/2 x k x e2
Elastic potential energy is measured in joules (J)
Spring constant is measured in Newtons per meter (N/m)
Extension is measured in meters (m)
Example: elastic potential energy = 1/2 x 4 x 22
8 J
Describe the energy changes of a catapault
elastic potential energy –> kinetic energy
What are the useful and not useful energy stores that a car transfers energy into
Useful energy transfers
Kinetic energy
Light energy
Not useful energy transfers
Sound energy
Thermal energy
What factors affect the size of the friction force acting between an object and the floor it is sliding over
The friction force increases if the object has a higher mass and if the surface of the object or the floor is rougher.
Lubricants, such as oil, wil reduce the size of the friction force by reducing the roughness of the surface
What are the two formula for calculating the eficiency of an energy transfer?
Efficiency = useful energy output/total energy input x 100%
Efficiency = useful power output/total energy input x 100%
Why do we try to make the energy transfers of machines as efficient as possible?
When a process is more efficient there is less energy dissipated as thermal energy and transferred into other not useful forms. This means that you do not have to put as much extra energy into the energy transfer to get the energy output that you want.
Explain why the efficiency of an energy transfer can never be more than 100%.
The law of conservation of energy states that energy cannot be created or destroyed. If an energy transfer was more than 100% then the energy output would be greater than the energy input. This means that energy would have to be created, which would break the law of conservation of energy.
What are the energy transfers of a kettle
electrical potential energy –> thermal energy, sound energy and kinetic energy