physics: energy test ⋆˙⟡

Label these unit prefixes

Definition of energy

A property of an object that allows work to be done e.g. movement

What is energy measured in

Joules (J)

Definition of system

Is known as one object or a group of objects being observed

Definition of closed system

An object or group of objects that can interact, but no energy or matter enters or leaves from the outside. The total energy in a closed system always stays the same.

What are the different types of energy

Kinetic, gpe, thermal, chemical, elastic, nuclear, magnetic, electrostatic

Where is kinetic energy usually found

Movement

Where is gpe usually found

Position above the ground

Where is thermal energy usually found

Temperature of the object, friction, air resistance

Where is chemical energy usually found

Fuel (food)

Where is elastic energy usually found

Anything stretched or compressed

Where is nuclear energy usually found

In nucleus of an atom

Where is magnetic energy usually found

Between the poles of magnets

Where is electrostatic energy usually found

Between charges

What are the energy transfers and pathways

Mechanical work, electrical work, heating, radiation

Mechanical work

A force moving an object through a distance

Electrical work

Charges moving due to potential difference

Heating

Due to temperature difference

Radiation

Energy transferred as a wave

What is the gpe calculation

GPE = m x g x h

What is GPE measured in

Joules (J)

How do you get from kilojoules to joules

x 1000

If you have a car and a truck and the cars velocity (speed) is 40m/s and the trucks velocity is 30m/s which has a higher kinetic energy

The truck as it has a larger mass that the car.

If you have a car 1 and car 2 and the car 1 velocity (speed) is 40m/s and the car 2 velocity is 30m/s which has a higher kinetic energy

Car 1 because it has a higher velocity (faster speed)

2 factors which affect KE of an object

• mass

• Velocity

  • the greater the mass and velocity the greater the KE

Equation for KE

What are the units of KE

What is the spring constant

A measurement of the stiffness in a spring

What is the spring constant measured in

N/m

What is the equation for elastic potential energy

What is the units for elastic potential energy

What is the equation to find the extension

Definition of elastic

A material that will go back to its original shape after the force has been removed

Definition of plastic or inelastic

A material that does not go back to its original shape after the force has been removed

Why is their limit of 12kg of weight when added to a spring hanging down

Because if more than 12kg is used the spring may break

What happens when ever work is done

When ever work is done energy is transferred

What always happens to a force

A force is always moved through a distance

Label this equation triangle for work done

Units for work done

Definition of power

Power measures the RATE at which work is done or the RATE at which energy is transferred

Definition of rate

How quickly

Equation for power

Units for power

Label this equation triangle for power

Definition of useful energy

Energy transferred to where it is wanted in the way that it is wanted

definition of wasted energy

The energy that us not usefully transferred - most commonly wasted energy is usually thermal energy

Definition of dissipation

The spreading out of wasted energy

As energy dissipates it becomes less and less useful

Where is energy usually dissipated to

Energy is often dissipated to the surroundings as thermal energy.

Definition of efficiency

How much of the total energy (power) is transferred to useful energy

Equations for efficiency

In equations what is efficiency given as

A decimal or percentage

Label this equation triangle for efficiency

Why can a device never be more than 100%

You cannot get more energy out of a device that you put into it. This goes against the law conservation that energy cannot be created.