Chapter #6 & #8 Flashcards
What is the definition of energy?
Quantity that must be changed or transferred to make something happen.
How does a person running a race use energy stores and transfers?
- At the start of the race, the runner’s muscles are STORES of chemical energy.
- As runner starts moving, chemical energy is TRASFERRED to kinetic and thermal energy.
What are the types of energy? (9)
- Kinetic energy (k.e.)
- Gravitational energy (g.p.e.)
- Chemical energy
- Nuclear energy
- Elastic energy
- Internal energy
- Thermal energy
- Electrical energy
- Mechanical (such as sound)
What is the definition of kinetic energy?
The energy store of a moving object
What is the definition gravitational potential energy (g.p.e.)? + an example.
Energy store of an object raised up against the force of gravity.
Ex. When a ball is thrown, the g.p.e. is largest at the top (and the k.e. is largest right before the ball hits the ground.)
What is the definition of chemical energy?
Energy stored in bonds between atoms that can be released when chemical reactions happen.
What is the definition of nuclear energy?
Energy stored in the nucleus of atoms.
What is the definition of elastic potential energy?
Energy stored in the changed shape of an object.
What is the definition of internal energy?
The energy of an object; the total kinetic energies of its particles.
What is the definition of thermal energy?
The energy transferred from a hotter place to a colder place because of the temp. difference between them.
What energies are energy stores? (7)
- Kinetic energy (k.e.)
- Gravitational potential energy (g.p.e)
- Elastic (strain) energy.
- Nuclear energy
- Internal energy
- Electrostatic energy
- Chemical energy
How is energy transferred?
It is transferred from one store to another.
What is an event (with energy)?
Something that happens or takes place, often at a specific time and place.
What is a process?
A series of actions or steps, often taking place over a long period of time.
What is the definition of Principle of conservation of energy?
Energy cannot be created or destroyed; it can only be stored or transferred.
What are the two most wasted energy?
Heat and sound
What are the two main ways heat energy is wasted?
- When fuels are burned
- Because of friction (when moving things or driving a car ect. and friction generates heat.
What are the main ways sound energy is wasted?
- Noisy machinery
- Loud cars
But, even loud sounds contain little energy so there is not much to be gained (in energy) by reducing it.
What is the definition of efficiency.
The fraction (or percentage) of energy that is usefully transferred.
What is the definition of lubricant?
Usually a liquid, it allows two surfaces to slide past each other more easily.
What is the definition of dissipated?
Energy that is spread out and not useful (wasted).
What is the equation for efficiency percentage?
useful energy output / total energy input x 100
What is the equation for efficiency?
useful energy output / total energy input.
What does an objects g.p.e. depend on?
- Its height above the ground => the higher the object, the greater its g.p.e.
- Its weight => the heavier the object, the greater force needed to lift it, hence the greater its g.p.e.
What is the value of gravity?
10N (9.8N)
What is the equation for ‘change in g.p.e.’?
weight x change in height
mg x change h
How do you make use of an object’s k.e.
By slowing it down.
e.x. moving air turns a wind turbine. This slows down air, reducing its k.e. The energy extracted can be used to turn a generator to produce electricity.
What two factors does k.e. depend on?
- The object’s mass => the greater the mass the greater its k.e.
- the objects speed => the greater the speed the greater its k.e.
What is the formula for motional k.e.?
1/2 x mass x speed ^2
Ek = 1/2 mv^2
If you know the g.p.e. and k.e. at any point of a ball being thrown, what is the total energy?
g.p.e. + k.e. = total energy
What is the unit for work done?
Joules
What is the unit for power?
Watts
What does ‘work done’ depend on?
- The size of the force => the greater the force, the more work is done.
- Distance moved in the direction of the force => the further it moves the more work is done.
How can ‘power’ be increased?
- Power can be increased by increasing the work done at any given time.
- Power can be in increased by reducing the time in which the same work is done.
work energy more less
When it moves an object, a smaller force does _____ work than a bigger force.
When it moves an object, a smaller force does more work than a bigger force.
work energy more less
The greater the distance an object is moved by the force, the ____ work it does.
The greater the distance an object is moved by the force, the more work it does.
work energy more less
Power is the rate at which _____ is transferred.
Power is the rate at which energy is transferred.
work energy more less
Power is the rate at which ____ is done
Power is the rate at which work is done.
work energy more less
The amount of work done is the amount of ___ transferred.
The amount of work done is the amount of energy transferred.
The work done vertically upwards is =
the g.p.e.
How much joules is 1 calorie?
4.18 joules
how do you calculate the distance when you have ‘work done’, ‘time’, and ‘force’?
d = W/F
What are the different ways that energy can be transferred?
- By force
- By heating
- By radiation
- By electrical current
How do you transfer energy by force?
- Force is provided when we provide kinetic energy (by providing force).
- When we lift an object (g.p.e.)
- When energy is transferred from one object to another by means of force, we say the force is doing work.
How do you transfer energy by heat?
From a hot object to its cooler surroudings.
How do you transfer energy by radiation?
Light reaches us from the sun. Some of the energy is transferred as infrared and ultraviolet radiation.
How is energy transferred by electrical current?
Electrical current is a convenient way of transferring energy from place to place.
What is an explanation of how energy is transferred through electrical current?
An electric current transfers energy from the chemical energy store of a flashlight battery to the internal energy of a bulb.
