Section 1 - Motion, Forces and Conservation of energy Flashcards
What properties do vectors have?
Magnitude and direction
What is magnitude?
Size
What are some examples of vector quantities?
Force, velocity, displacement, weight, acceleration, momentum.
What properties do scalars have?
Magnitude ( no direction )
What are some examples of scalar quantities?
Speed, Distance, Mass, Energy, Temperature, time.
What is distance?
how far an object has moved
( scalar )
What is displacement?
The distance and direction in a straght line from an objects starting and finishing point.
( Vector )
What is speed?
How fast you are going
( scalar )
What is Velocity?
How fast you are going in a given direction.
( Vector )
What is a acceleration?
The change in velocity in a certain amount of time
What is deceleration?
negative acceleration
What is the uniform acceleration due to gravity?
10 m/s2
what is the typical speed for sound in air
340 m/s
Why is acceleration a vector?
it is measuring a change in another vector
What is the equation of average speed?
total distance/time for whole journey
How do you work out the gradient of a line on a graph?
vertical difference/horizontal difference
( resultant forces )
What is Newtons first law?
a moving object will continue to move at the same speed and direction unless an external force acts upon it / A stationary object will remain at rest unless an external force acts on it
A resultant force is needed to change motion
What is a resultant force?
When there is an overall force on an object
What is balanced forces?
When there is no reslultant force
Forces acting on THE SAME object
What does newtons first law mean?
A force is needed to change motion
What is newtons 2nd law?
a resultant force ensues an object to accelerate
What is the equation regarding force, mass and acceleration?
f = ma
What is newtons 2nd law mean?
Acceleration is proportionate to the resultant force and the mass of the object
What is newtons 3rd law?
when 2 objects interact, there is always a pair of forces present, known as action-reaction forces
What are action reaction forces
forces of the same size, type and in opposite
One object acting on another
What are some energy stores?
Kinetic
Thermal
Chemical
Grav Potential
Elastic Potential
Electrostatic
Magnetic
Nuclear
What are kinetic stores?
Anything moving has energy in its kinetic store
What are Thermal stores?
any object - the hotter it is, the more energy it has in this store
What is a chemical store?
anything that can release energy by a chemical reaction e.g. food, fuels
what are Grav potential stores?
anything in a Grav field
What is elastic potential?
anything streched , like springs, rubber bands
What is electrostatic or magnetic stores?
Two charges that attract or repel each other
What are neuclear stores
atomic nuclei release energy from this store in nuclear reactions
When can energy be useful?
when it is transferred to a usefull store
what reduces rate of energy transfer by heating?
Insulation e.g. walls with air gaps
Energy Transfers
pathways for transferring energy
When an object is moving, where is the energy stored? How does this increase and decrease?
Kinetic energy store
, when it speeds up energy is transferred into this store and is the released when it slows down
This depends on mass and speed
What happens to kinetic energy if you double the mass?
It doubles
What happens to kinetic energy is you double the SPEED?
it quadruples, this is due to the speed being squared in the kinetic energy equation
An object at a height has energy in what store?
GPE
What does conservation of energy mean?
Energy never increases or decreases
What are the 4 main ways energy can be transferred?
Mecanially, electrically, by heating or radiation
Energy transferred mechanically
A force acting on an object ( and doing work)
Energy transferred electrically
a charge doing work
Energy transferred by heating
energy transferred from a hotter object to colder object
Energy transferred by radiation
Energy transferred by waves
Energy transfered when a ball rolls up a slope
The ball does work against the gravitational force, so the energy is transferred mechanically from the kinetic energy store of the ball to its GPE.
Energy transfered when a bat hits a ball
A bat has energy in its kinetic energy store. Some of this is transferred mechanically to the balls kinetic energy store. some of the energy is also ransferred mechanically to the thermal energy stores of the bat and the ball. The rest is dispersed through sound.
Energy transfers when a rock is dropped from a clifff.
( assuming theres no air resistance), gravity does the work on thr rock, so the rock constantly accelerates towards the ground. Energy is transferred mechanically from the rocks GPE to the KE store.
Energy transferrs in a car slowing down ( without brakes)
Energy in the KE store of the car is transferred mechanically ( due to friction between the tyres and the road), and then by heating, to the thermal energy stores of the car and road.
Energy transfers a kettle boiling water
Energy is transferred electrically from the mains to the heating element of the kettle, and then by heating to the thermal energy store of the water.
What are the main 2 ways to reduce unwanted energy transfers?
Lubrication - reduces friction
Insulation - reduces energy transfer by heating
How is unwanted energy transfers created in mechanical work?
Whenever soemthing is done mechanically, frictional forces to be done, including moving parts rubbing together, and air resistance. The energy needed to overcome these frictional forces is transferred to the thermal energy stores of whatever is doing the work and the suroundings
How does lubricants increase efficiency?
For objects that are toucning eachother, lubricants can be used to reduce the friction between the objects surfaces when they move.
E.g. oil or other liquids
Conduction
When oneside of the object is heated, the particles in the hotter part vibrate more and collide with eachother. this transfers energy from their kinetic energy stores, which vibrate faster and transfer energy through the object.
What is thermal energy a mesure of?
how well a material transfers energy by conduction. E.g metals have a high conductivity and air has a low condcutivity.
Insulation reducing energy loss by heating in houses.
In a building, the lower thermal conductivity of its walls, the slower the rate of energy transfer through them ( the building will cool more slowly)
Prevention of heatloss in housing
- cavity walls reduce
- the thicker the walls, the slower rate of energy transfer.
What are the non-renewable energy sources
Fossil fuels and nuclear fuel
Fossil fuels and nuclear fuel
benefits and negatives
- Reliable and easily accessable at short notice
- Cheap to extract/run
- Fossil fuels are slowly running out
- Environmental damage
Fossil fuel and nuclear fuels
Environmental problems
Fossil fuels release CO2 when burned which adds to the greenhouse effect, increasing global warming
Burning coal and oil releases sulfur dioxide which leads to acid rain - reduced by extracting the gas or cleaning it up
Oil spillages and nuclear waste
Examples of renewable energy recources
Bio-fuels
Wind
The sun
Hydro-electricity
Tides
Renewable recources benefits and downsides
- renewable
- Still do damage the environment
- Dont provide as much energy and can be unreliable due to the weather
Bio-fuels
Renewable energy resources created from either plant products or animal dung. Can be any state and can be burnt to produce energy or run cars in the same way as fossil fuels.
Bio-fuels benefits and disadvatages
- only Carbon neutral if tou burn them at the same rate as growing things
- Reliable, but cannot respond to immediate energy demands
- High cost and low space
- Areas of forest cleared for growth of bio fuels- CO2 emmisions and methane
Wind power B+D
- generator with wind pushed blades so no
- High initial cost but low runnign cost
- noisy and spoil view
- Conditional to wind
Solar cells B + D
- made from materials hat use energy transferred by light to create an electric current
- used in remote places to power road lights and satteligts
- high initial cost but no runnign cost
- Small scale electricity
- Conditional on sun
HE B+P
made by flooding a valley by building a big dam, rainwater is caught and allowed out through big turbines
No pollution but environmental damage through the flooding of the valley - loss of habitat
Immediate response to energy demand
Tidal barrages
- big dams built across river water let in trhough turbines
How do you interpret adistance/timegraph?:
- Gradient
- Flats
- Curves
- Gradient - Steady speed (calc)
- Flats - Stopped
- Curves - accelerating
How do you interpret avelocity/timegraph?:
- Gradient
- Flats
- Curves
- Area under the graph
- Gradient - Acceleration
- Flats - Steady speed
- Curves - Changin acceleration
- Uphill/downhill - Accelerating
- Area under the graph - Distance travelled
What is mass?
the amount of stuff in an object, mesured in a scalar quantity (Kg by a mass balance)
What s weight?
the force acting on an object due to gravity/ the pull of the gravitational force on the object - Mesured in Newtons (N)
How is weight mesured?
A calibrated spring balance ( Or newton meter)
Does weight change with location?
Yes, depending on the gravitational field strength
What happens with velocity if an object is travelling in a circle?
Because of the circular travel, it is contantly changing direction, so it is constantly changing velocity, this means it is accelerating.
What is centripetal force?
the resultant force - causing the acceleration (velocity change in direction) - this acts towards the centre of the circle
What is inertia?
the tendncy for motion to** remain unchanged**
= newtons 1st law - objects at rest will stay at rest, objects in motion will stay in motion
In F=ma, is anything directly proportional?
F = a
the size of the resultant force is directly proportional to the acceleration it causes
What does Inertial mass mesure?
How difficult it is to change an objects velocity
How do you find inertial mass?
F/a =
so basically the ratio of how much force per acceleration
Examples of inertial mass?
Moon will have a large inertia = lots of mass = requires a really big force to change its velocity
What is newton’s 3rd law?
when 2 objects interact, the forces they exert on eachother are equal ( Magnitude) and opposite (direction)
if you push on something, that thing will push back with a force called a normal contact force. Whoever has lower inertia then moves
What is momentum?
The product of the object’s mass and velocity
P (mom) = Mass x Velocity
What is the standard unit for mass?
Kg
What is the standard unit for velocity?
m/s
What is the standard unit for Momentum?
Kg m/s
How does a force cause a change in momentum?
Newtons 2nd law:
- Resultant force causes and object to accelerate
Force = Mass x acceleration
Acceleration is ΔV / T
So force = (mv - mu) / T
Which is change in momentum / time
How does force affecting momentum apply in the real world?
If someones momentum changes rapidly, (e.g. car crash) the forces will be very large, and likely to cause injury
What is the equation for stopping distance ?
Thinking distance + Braking distance
What is thinking distance affected by?
Reaction time - Increased by tiredness, distractions, drugs or alcohol
Speed - Faster youre going, the gurther youll travel during your reaction time
What is Braking distance affected by?
Distance taken to stop once brakes have been applied
- Speed - faster = longer
- Mass - Heavier = More momentum = longer
- Condition of brakes - worn/faulty wont be able to break with as much force
- Friction - Skid if dirty, icy or wet or the tires are bald
How do u test reaction time?
Ruler test
