Topic P1 - Energy Flashcards
What is Energy?
It is the ability for an object to do work.
When work is done by an object energy is transferred?
From the object e.g. when a balloon pops the air inside it does work to surrounding air.
When work is done on an object energy is transferred?
To the object e.g. When a man pushes a box, he is transferring energy to the Box.
What is Energy measured in?
Joules (j)
1 ( kilojoule ) equals how many joules?
1000J
Convert 9 KJ to joules?
9000 joules (j)
9 J equals how many kilojoules
0.009 KJ
1 Megajoule equals how many Joules?
1,000,000 J
What is the Pneumonic to learn the 8 stores of energy?
Geeks Lunch(heat = thermal and U doesn’t stand for anything.
What are the 8 stores of energy?
1) Kinetic energy
2) Thermal
3) Gravitational potential energy
4) Elastic potential
5) Chemical
6) Magnetic
7) Electrostatic
8) Nuclear
What is Thermal energy also known as?
Internal energy.
What are the 4 pathways energy can be transferred from?
1) Mechanical ( forces doing work)
2) Electrical ( using electrical currents)
3) Heating ( temperature difference)
4) Radiation ( light or Electromagnetic)
What is a System?
A system is an object or a group of objects.
Identify the systems, and energy changes in a catapault ready to fire a ball?
Our system is the catapault and the ball, the energy starts in the elastic store within the catapault. When it is fired the energy is transferred along the Mechanical pathway, most of it will go the kinetic store of the ball, some will go into thermal store of catapault ( the elastic will warm up)
What is the Conservation of energy?
Energy cannot be created or destroyed, only transferred between a system.
What are closed systems?
Are systems where neither matter nor energy can enter or leave.
If a ball is thrown into the air with O Joules of Gravitational potential energy and 10 Joules of kinetic what is the amount of GPE and kinetic when the ball is stationary?
When it is about to start falling the ball has 10 J of GPE and 0 joules to the kinetic energy.
Describe the energy transfers when a ball is thrown vertically upwards?
Energy is transferred from the kinetic energy store to its gravitational potential energy store.
Describe the energy transfers when kicking a football?
Energy is transferred from the chemical store in our bodies to the kinetic energy of our foot, which in turn is transferred directly to the Kinetic energy of the ball.
Describe the energy transfers of a wind- up toy?
Energy is transferred from the Elastic potential store of the spring inside to its Kinetic energy store.
Describe the energy transfers when we heat water inside a kettle?
Energy is transferred electrically to the thermal store of the water.
Describe the energy transfers when a driver breaks and decelerates the car to rest?
Its kinetic energy is transferred to the thermal energy store in the brakes and temperature of brakes increase.
Describe the energy transfers when two like poles repel of magnets?
Energy will be transferred to the magnetic energy store to the kinetic energy store of both magnets.
Describe the energy transfers when we burn wood in a fire?
Energy is transferred from the chemical store of the wood to the thermal store of the surrounding air.
Describe the energy transfers when we power a filament bulb using a battery?
Energy will be transferred from chemical energy store of battery, to thermal store of filament.
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
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.
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
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.
If an object is more higher up what does this mean?
Higher GPE
Describe the energy transfers that occur when the wind causes a windmill to spin?
Energy is transferred mechanically from the kinetic energy store of the wind to the kinetic energy store of the windmill.
Explain why your hands get hotter when you rub them together
When you rub your hands together the force of friction acts over a distance. This causes the transfer of energy from chemical store to the thermal store, this makes your hands heat up.
Explain why a roller coaster cannot roll up the track to the same height as the peak that it has just come from
This is due to energy dissipation as thermal energy into the environment. When the roller coaster rolls down the track some of the energy is dissipated out of the system as thermal energy. This means that the total energy in the system has reduced, reducing the maximum gravitational potential energy it can gain
What is the Equation for Kinetic energy and units?
KE = 1/2 x m x v2
Mass is measured in kilograms (kg)
velocity is measured in meters per second (m/s)
Kinetic energy is measured in joules (J)
A car of mass 1500 kg is travelling a speed at 20 m/s . Calculate its Kinetic energy?
KE = 1/2 x m x v2
= 1/2 X 1500 X 20 sqaured
= 15000 J
What is Limit of Proportionality?
The spring has been stretched so much that it cannot return to its original length.
What is the Equation of Elastic potential energy and what are the units?
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)
A steel spring constant 5 N/M is initially 10 cm long. Calculate the increase in the Elastic potential energy when it is increased by 15 cm ?
EPE = 1/2 x k x e2
e = 5 cm = 0.05 m
1/2 X 5 X 0.05 squared = 0.00625J
What is the Equation of Gravational potential energy and what are the units?
Gravitational potential energy = mass x gravitational field strength x height
GPE = m x g x h
Gravitaitonal potential energy is measured in Joules (J)
Mass is measured in kilograms (kg)
Gravitational field strength is measured in meters per second squared (9.8 N/Kg)
Height is measured in meters(m)
A book of a mass of 400 g is lifted from the floor onto a 1.2 m high shelf. Calculate the increase in GPE of the book. Take G = 9.8 N/Kg?
m = 0.4 kg
0.4 kg x 1.2 X 9.8 = 4.7 J
When a Object falls its Gravitational potential energy stored is transferred where?
To its kinetic energy store
What is Air resistance?
It is the friction between the air and an object
For a falling object when there is no air resistance energy lost from Gravitational potential energy is store equals what?
Energy gained in the kinetic energy store.