CH1 Energy transfers and efficiency Flashcards
(30 cards)
Name 8 types of energy
-Chemical
-Kinetic
-Gravitational Potential
-Elastic
-Electrical
-Thermal energy
-Electrostatitc
-Nuclear
Units for energy
Joules
Which of these happens to energy?
a. converted
b. destroyed
c. created
a. converted
What energy is movement energy?
Kinetic
How to calculate efficiency
(useful energy output/ total energy in) x 100
Units for energy
Joules
Main useful energy transfer in cars?
Chemical to kinetic
a) when a ball falls in air it loses ______ energy and gains _____ energy.
b) when an electric heater is switched on, it changes _____ energy into ______ energy.
a) gravitational potential, kinetic
b) electric, thermal
name 4 types of energy transfer
mechanical
electrical
heating
radiation
What is the loss of energy called
dissipation
State the law of conservation of energy
Energy cannot be created or destroyed, only transferred
An exciting fairground acts like a giant catapult. The capsule which you are strapped in, is fired high into the diy by rubber straps . Explain the energy transfers taking place.
Elastic -> kinetic -> gravitational potential -> kinetic -> elastic
Why does a pendulum eventually stop?
The pendulum loses energy little by little from air resistance and friction.
What is the equation for kinetic energy?
1/2 x mass x speed^2
OR
1/2mv^2
An apple of mass 100g falls from a tree.it reaches a speed of 6 m/s before landing on Isaac’s head, what is gain of the kinetic of the apple
Ek = 1/2mv^2
Ek= 1/2 x 0.1 x 6^2
Ek= 1.8J
How much kinetic energy does a 30kg dog have when it runs at 4m/s
Ek = 1/2 x 30 x 4^2
Ek = 240J
What is a system?
an object or a group of objects that can be identified
What is a closed system?
A system where no energy is added and none can escape
What is work done
energy transferred when a force moves an object
work=forcexdistance
What is 1 joule of work
the work done when a force of 1N causes an object to move 1m in the direction of the force
describe the energy transfer when a moving car slows down
energy is transferred mechanically from the kinetic store of the far to the thermal store of its brakes- some energy is dissipated to the thermal store of the surroundings
describe the energy transfer when a kettle is used to heat water
the electric current in a kettle transfers energy to the heating element’s thermal store- energy is then transferred by heating from the heating element’s thermal store to the thermal store of the water
describe the energy when a ball is fired using an elastic band
energy is transferred mechanically from the elastic store of the elastic band to the kinetic store of the band- some energy is dissipated to the thermal store of the surroundings
describe the energy transfer when a battery powered toy car is used
energy is transferred electrically from the chemical store of the battery to the kinetic store of the toy car- some energy is dissipated to the thermal store of the surroundings
