Physics Chapter 1+2 Flashcards
Chemical energy stores
Found in food, fuels and chemicals in batteries
Energy is transferred during chemical reactions
Kinetic energy
Energy of an object because it is moving
Gravitational potential energy
Energy stored in an object because of its position
Elastic potential energy
The energy stored in a springy object when you stretch or squash it
Thermal energy
The energy in an object because it has tempreture
When an object falls….
…. it gains speed, its store of gravitational energy decreases and its kinetic energy store increases. When it hits the floor its kinetic energy store decreases, some or all of its energy is transferred to its surroundings, the thermal energy in the surrounding increases becaise of the friction on impact.
Why the pendulum loose momentum and not reach its max gravitational energy when you swing it
Because of the air resisting it. If it was in a vacuum it would keep swinging forever
Formula for work done
Work done (J)=force applied (N) x distance moved along the line of force (M)
Formula for change in objects gravitational energy store (J)
=weight (N) x change of height (m) [gravitational field strength (N/Kg)]
Formula for kinetic energy
=1/2 x mass (kg) x speed^2 (m/s)^2
Formula for elastic potential energy
=1/2 x spring constant (N/m) x extension^2 (m)^2
Formula for efficiency (%)
=useful output energy transferred by the device/total input energy supplied to the device
x100
What is efficiency
How useful an object is
What percentage of the energy in useful energy
How to increase efficiency
Insulation to stop heat being wasted
Lubrication to reduce friction
What is power
The rate of transfer of energy
What is the formula for power(w)
=energy transferred to the appliance(J)/time takes for the energy to transfer (s)
Formula for efficiency (%) in terms of power
=useful power out/total power in x100
What is the best conductor of energy
Metal
What non metals are the best insulators
Wood and fibreglass
What is specific heat capacity (SHC)
The energy needed to raise the temp of 1kg of the substance by 1°C
Formula for SHC
=energy transferred(j)/mass(kg)x temp change (°C)
How do you find the SHC of an object
With joule meter and a thermometer to find temp change and energy transferred then pit it into the formula
What is cavity wall insulation
Is insulation material put in between the two brick layers of an external house wall
How can the rate of energy transfer in a house be reduced
Loft insulation
Cavity wall insulation
Double glazed windows
Aluminium foil behind radiators
