Physics Year 9 - Chapter 1 - Conservation and dissipation of energy Flashcards
The specific heat capacity of a substance is the energy needed to …
raise the temperature of 1 kg of a substance by 1 degrees
When an object is moved by a force, work is done on the object by the force. So the force ——— to the object.
transfers energy
What happens to the energy transferred by a rower in a boat?
chemical (body)
mechanical (oars)
friction (water against the boat)
Anything that is moving has energy in its ———- store
kinetic energy
Energy can’t be ——– or ————
created or destroyed
Describe the changes in energy stores that take place when food is heated in microwave oven.
Electrical - makes microwave work
Electrical to cook food
Heat energy comes off the microwave
Light energy and sound waste
Energy is transferred
mechanically (by force doing work)
electrically (work done by moving charges)
heating or radiation (eg. light or sound)
waves
Describe the changes in energy store of an electric train as it approaches a station and brakes to a halt
- waste of sound and heat
- electrical applies the breaks
- mechanical between the break disks and break pads
- thermal between break pads and disks
Describe the changes to the energy stores of a ball when it falls and rebounds without regaining its initial height
- gravitational potential energy (up high)
- as it drops losing gravitational potential but gains kinetic
- when it hits the ground it has maximum kinetic
- as it goes up it loses kinetic and gains gravitational but it has gravity and friction working against it so it doesn’t return to its original height.
Force you need to lift up an object = …………………
the weight of the object
Energy is never used up. Instead it is —————–
just transferred between different energy stores and different objects
When an object falls and gains speed its store of gravitational potential energy DECREASE/INCREASE
and its kinetic energy store DECREASE/INCREASE
decrease
increase
Why is the speed of a miner at the bottom of the slide much less than the calculated maximum possible speed?
- Against friction between the miner and slide.
- Slide isn’t perfectly smooth or miners clothes rough
- Causes kinetic energy to be transferred as heat
- loss of air resistance.
Changes in energy transfer of an object when it falls and hits the ground.
- gravitational potential energy store
GOES TO
- kinetic energy store
THEN
- energy transferred to the surroundings eg. sound waves AND increase in thermal energy stores to surroundsHot things have MORE/LESS kinetic energy as they cool down they have MORE/ LESS the average energy of particules.
more
lower
Heat energy always goes from a hot body to a cold body.
When a roller coaster gets to the bottom of a descent, describe the energy transfer and changes to energy store that happens
As it goes DOWN it gains kinetic energy and when the breaks are applied it becomes heat, sound and mechanical energy.
At the BOTTOM
- mechanical energy on breaks
- heat energy, heat from friction
- sound energy noise from breaks breaking
When an object moves down, the energy in its gravitational potential energy store INCREASES/DECREASES
decreases
Change in energy stores in a candle
- chemical (lighting it)
- Light (mechanical working)
- waste energy
The work done by a force depends on __________
The size of the force and the distanced moved
Describe the energy stores of an electric train as it moves UP a hill at a constant speed
- mechanical energy (wheel and track)
- electrical powers the train
- gravitational - pushes down on the train
A car is brought to a stand still when the driver applies the breaks. Explain why the break pads become warm
- Friction between the break pads and the wheel discs oppose the motion of the wheels
- Energy is transferred from the kinetic energy store of the vehicle to the thermal energy store of the brake pads and wheel discs
A catapult is used to fire an object into the air. Describe the energy transfer when the catapult is
1 stretched
2 released
- elastic to mechanical (body)
2. elastic to kinetic (the spring is contracting, kinetic is increasing)
What happens to the energy transferred by an electric motor used to raise a car park barrier
Electrical energy then mechanical as it moves up
The greater the mass of an object the SLOWER / FASTER it’s temperature DECREASES / INCREASES when its heated
slower
increase
