Chapter 1 🤙🏻 Flashcards
How is energy transferred?
By: waves
An electric current
A force when an object falls
What is the principle of the conservation of energy?
Energy cannot be created or destroyed
What is a closed system?
A system where no energy transfers take place
What is work done?
The amount of energy transferred to an object
When a force makes an object move
What is the equation for work done?
Work done= force applied x distance moved along the line of the action of the force
What is the equation for the change in gravitational potential energy store?
Change of gravitational potential energy store= mass x gravitational field strength x change of height
Why does the gravitational potential energy store of an object increase when it is lifted?
Work is done to overcome the gravitational force
What is the power supplied to a motor?
The energy supplied to it
What makes an appliance powerful?
The faster it transfers energy
How to calculate power (W) using energy transferred and time?
Power = energy transferred / time
How to calculate use power wasted by an appliance?
Wasted power = total power input - useful power output
Useful energy from a light bulb
Light
Wasted energy in a light bulb
Heat
Useful energy in a heater
Heat
Wasted energy from a heater
Light emitted from glowing element
Useful energy in a toaster
Heat
Energy wasted from a toaster
Heating the toaster itself
Useful energy in a kettle
Heat water
Wasted energy in a kettle
Heating kettle itself
Useful energy hairdryer
Heat
Kinetic energy of fan
Wasted energy from a hairdryer
Sound
Heating hairdryer itself
Useful energy in motor
GPE of objects lifted
Kinetic energy
Energy wasted from motor
Heating motor
Sound
What should an electrical appliance do?
Waste as little energy as possible
What is the input energy?
The energy supplied to a device
What is the greatest efficiency a decide can have?
100%
How do machines waste energy?
Friction between moving parts
How to reduce problem of friction?
Lubricants moving parts
How to reduce problem of resistance?
Use wires with lower resistance
How to reduce problem of air resistance
Streamline
How to produce problem of sound being transferred to surroundings
Tighten loose parts
What is useful energy?
Energy transferred to where it is wanted in the way it is wanted
What is wasted energy?
Energy they isn’t usefully transferred
What happens when energy dissipates?
It spreads out
What is the equation for kinetic energy (J) using mass and speed?
Kinetic energy = 1/2 x mass x speed ^2
What is the equation for elastic potential energy using Spring constant, 1/2 and extension?
Elastic potential energy = 1/2 x Spring constant x extension^2
what are the 8 energy stores?
chemical kinetic elastic potential gravitational potential thermal nuclear magnetic electrostatic
examples of chemical energy stores (3)
fuels
foods
chemicals in batteries
when is energy in a chemical energy store released?
during chemical reactions
what is a kinetic energy store
the energy an object has because it is moving
what is the gravitational potential energy store?
the energy an object has because of its position above the ground
what is the elastic potential energy store
the energy stored in a springy object when you stretch or squash it
what happens when a system changes?
energy is transferred
what changes happen to the energy stores when a ball is dropped?
gravitational potential energy decreases
the kinetic energy increases
what is a closed system?
where no energy can enter or leave
what energy is transferred when a person throws a ball up?
chemical energy in a person is transferred to kinetic energy in the ball
what happen when you apply the brakes in a car
the friction causes the kinetic energy to decrease and be transferred as heat energy to the surroundings
what happens when an object is moved by a force?
work is done on that object by the force/ the force transfers energy to the object
what does work done equal?
energy transferred
why do the brake pads become warm when yoy apply them?
work is being done to overcome friction
Why does an object speed up as it falls?
GPE store is converted to kinetic energy
Why wouldn’t a bungee jumper return to the original height after a jump?
Some energy has been transferred to the surroundings
Why would a pendulum swinging in a vacuum be an example of a closed system?
There is no energy transferred so it could keep on swinging forever
What is work done the same as
Energy transferred
What happens to work done to overcome friction?
It is transferred to the surroundings
What energy transfers happen when an object is lifted up?
The work done on the object is equal to the increase in GPE
What does work done to move an object up or down depend on? 2
How far
Weight
To calculate difference in GPE along a slope what do you remember to do
Calculate vertical height not distance up slope
Why does the GPE of an object increase when you lift it up
Work is being done to overcome gravity
Energy lost from GPE store =
Energy gained in kinetic energy store
What does the kinetic energy of a moving object depend on
Mass and speed
What is elastic potential energy
Energy stores in an elastic object when work is done on the object
What is useful energy
Energy that is transferred in the way that is wanted
What is wasted energy?
Energy that isn’t usefully transferred
What does it mean when energy dissipates
It spreads out and is stores in less useful ways
What is the input energy
The energy supplied to a device
What are the 4 reasons machines waste energy
Noise
Friction
Air resistance
Electrical resistance
How to reduce energy lost by friction
Lubricate moving parts
How to reduce energy lost by electrical resistance
Use wires with as little resistance as possible
How to reduce energy lost by air resistance
Streamlining
How to reduce energy lost by sound
Cut out noise
What is the power supplies to a motor
The energy supplied to it per second
The more powerful an appliance is….
The faster it transfers energy
