Physics Flashcards
Law of conservation of energy
Energy cannot be created or destroyed, it can only be transferred from one store to another
Examples of energy conservation
A bat hitting a ball
Electric heater
Rollercoasters
What is energy measured in
Joules
Gravitational potential energy
Amount of energy an object has because of its position above the ground
Spring constant
Numerical value of the stiffness of the spring
Hooke’s law
The extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded
Efficiency limits
No device can be more than 100% efficient because you cannot create energy
Thermal conductivity
The rate which an object transfers heat energy
Heat
Amount of energy stored in an object or substance
Infared radiation
A type of electromagnetic wave which transfers heat energy
A black body
Object that absorbs all of the radiation that hits it
Black body radiation
Radiation emitted by a perfect black body
Specific heat capacity
The energy needed to raise 1kg of material by 1 degree celsius °C
Which substance temperature increases quicker, oil or water
Oil
Factors of insulators
Poor conductors of heat (heat isn’t easily transferred away)
An insulator doesn’t transfer heat very well which means it stays where it is for longer
Where is natural gas found
In rock formations deep below the surface of the Earth
Advantages hydroelectric power
No pollution
Reliable
Dams are designed to last for many decades
Disadvantages hydroelectric power
Very expensive to build
Natural habitats destroyed
Must operate for decades before profitable
Wave power
A wave generator uses wave motion to make a generator move up and down
This turns the generator to generate electricity which is transferred to the shore via a cable
Tidal power advantages
No pollution
Infinite resource
Free energy resource
Disadvantages of tidal power
Cost of setup
Can disrupt sea life
Generation is for a short periods at tide peaks
Wave power advantages and disadvantages
Same as tidal wave
Similarities solar cells and solar heating panels
Both use solar energy from sun
Both can be used domestically
Unreliable depending on weather conditions
Differences solar cells and solar heating panels
Solar cells produce a current, solar heating panels heat water
Solar heating panels more efficient when using energy to heat water
Solar cells can connect to national grid solar heating panels can’t
Renewable resources
Tidal
Hydroelectric
Solar
Goethermal
Wind
Wave
Biofuel
Non-renewable resources
Coal
Oil
Natural gas
Nuclear
Order of what causes greenhouse gas emissions
Gas
Oil
Coal
Advantages nuclear power
No greenhouse gases
Much more energy transferred from each kg uranium
Disadvantages nuclear power
Used fuel rods contain radioactive waste
An explosion in a reactor could release radioactive material
Advantages renewable energy
Will never run out
Don’t produce greenhouse gases
Don’t create radioactive waste products
Disadvantages renewable energy
Some renewable resources are not available all time
Some resources can be unreliable
Wind turbines create noise that upset people nearby
Displacement
Distance without change in direction
Vector
Physical quantities with size and direction
Scalar
Physical quantities with size but no direction
Force
A push or a pull acting on an object due to interaction with another object
3 examples of contact forces
Friction
Air resistance
Tension
3 examples of non-contact forces
Gravitational
Electrostatic
Magnetic
3 examples of vector quantities
Velocity
Displacement
Force
Acceleration
Momentum
3 examples of scalar quantites
Temperature
Time
Mass
Speed
Distance
Energy
Resultant force
A single force equivalent to all other forces acting on a given object
The conservation of momentum
Within some problem domain, the amount of momentum remains constant
Inertia
The tendency of an object to continue in its state of rest, or in uniform motion unless acted upon by an external force
Why the egg is less likely to break when dropped onto soft foam rather than onto a concrete floor
Soft foam absorbs impact better than concrete because it compresses upon impact
Soft foam dissipates the kinetic energy of the falling egg over a longer period of time as it compresses
Concrete does not dissipate the kinetic energy as effectively, leading to a more abrupt stop upon impact and a higher force exerted on the egg
Soft foam provides a cushioning effect due to its flexibility, which helps to decelerate the egg gradually upon impact
Soft foam made of materials which help mitigate force of impact
Explain the changing motion of the skydiver in terms of the forces acting on the skydiver
Gravity pulls the skydiver downwards
As skydiver falls they accelerate due to the force of gravity
As the skydiver’s speed increases they encounter air resistance
Force of air resistance becomes equal to force of gravity acting on skydiver leads to terminal velocity
When skydiver deploys parachute air resistance increased
Explain why atmospheric pressure decreases with increasing altitude
Most atmosphere’s molecules held close to earth’s surface by gravity
Lever
A rigid body capable of lifting a heavy load with a small effort
Acceleration
Its change of velocity per second
Weight
The force of gravity acting on an object
Terminal velocity
The maximum velocity that an object can travel in a fluid
Thinking distance
Distance travelled in between the driver realising he needs to brake and actually braking
Braking distance
The distance taken to stop once the brakes are applied
Momentum
A property of a moving object which depends on how much mass the object has and how fast it is moving
Compression
Caused by pushing forces
This can be done by pushing the two ends of the spring together
Tension
An object that is being stretched experiences a tension force
Proportional
Where 2 quantities affect each other
What happens if spring pass its limit of proportionality
The spring extension will no longer be proportional to the load
Pressure
Force per unit area
Why a water dam has a thicker base than top
So water pressure is very large at the bottom due to its large depth
Upthrust
The upward force that a liquid or gas exerts on an object floating in it
Archimede’s principle
An object totally or partially immersed in a fluid is subject to an upward force equal in magnitude to the weight of fluid it displaces
How does an object float
When its weight is equal to the upthrust provided by the fluid
When does an object sink
When its weight is greater than the upthrust provided by the fluid
