Chapter 1 - Motion, Forces and Conservation of Energy Flashcards Preview

Physics GCSE (CJ) > Chapter 1 - Motion, Forces and Conservation of Energy > Flashcards

Flashcards in Chapter 1 - Motion, Forces and Conservation of Energy Deck (53):

What is the difference between a vector and a scalar quantity?

A scalar measurement is just a magnitude but a vectors have a magnitude and a direction.


What is displacement?

The distance and direction from an object's start point to it's finish point.


What can you measure a vector direction as?

Relative to a point (e.g. towards the road) or as a bearing


What is the equation for speed (m/s)

Distance travelled (m)/Time (s)


What is uniform acceleration?

Accelerating/decelerating at a constant rate


What is the equation for acceleration (m/s^2)

(v-u)/t where v=final velocity, u=starting velocity and t=time


What is the equation for uniform acceleration?

v^2-u^2=2ax where v=final velocity, u=starting velocity, a=acceleration and x=distance


What does the gradient describe on a distance/time graph?

The speed of an object. Curves represent acceleration. A straight line means a constant speed


How do you work out the speed on a distance/time graph?

If it's a straight line, the speed is equal to the gradient of the line but if it's curved, then you draw a tangent and find the gradient of it (that only tells you the speed at that moment). For average speed, you simply do total distance travelled/time taken


What does the gradient describe on a velocity/time graph?

The acceleration of an object. A curve means it is an increasing/decreasing acceleration.


How do you work out the distance travelled on a velocity/time graph?

The area under any section of the graph is equal to the distance travelled in that time section


What is Newton's First Law?

If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it will remain moving at the same velocity.


What is Newton's Second Law?

Force = mass x acceleration. The resultant force and the acceleration of an object are directly proportional but the mass and acceleration of an object are inversely proportional


What is Newton's Third Law?

When two objects interact, the forces they exert on each other are equal and opposite


What is the difference between weight and mass?

Mass is the amount of matter in an object and it will have the same value anywhere in the universe. Weight is the force acting on an object due to gravity and is measured in Newtons (N).


What is the equation for weight?

mass (kg) X Gravitational field strength (N/Kg)


What is centripetal force?

If an object is travelling at the same speed in a circle, the velocity is constantly changing and the resultant force acting towards the centre of a circle. The centripetal force is the force that keeps something moving in a circle.


What is inertia?

The tendency to keep moving with the same velocity. E.g. objects at rest stay at rest (Newton's First Law)


What is the inertial mass of an object? How can it be calculated?

A measurement of how difficult it is to change the velocity of an object. It can be calculated using Newton's Second Law


What is the equation for momentum

p=mXv where p=momentum (kg m/s), m=mass (kg) and v=velocity (m/s)


Is momentum a scalar or a vector quantity?

Vector - always include a direction


What is the Conservation of Momentum?

the fact that the total momentum before = the total momentum after


What is the equation for change in momentum?

Force(N) = change in momentum (Kg m/s)/Time (s)


What is the stopping distance of a car?

The distance covered between the driver first spotting a hazard and the vehicle coming to a complete stop.
Stopping distance = thinking distance + braking distance


What is thinking distance and what might affect it?

The distance travelled in the reaction time (noticing the hazard to applying the brakes). It is affected by:
Your reaction time - increased by tiredness, alcohol, drugs and distractions
Your speed - the faster you’re traveling, the further you’ll go in your reaction time


What is the braking distance and what might affect it?

The distance taken to stop once the car has applied the brakes. It is affected by:
Your speed - the faster you’re traveling, the longer it takes to stop
The mass of the car - a heavier car will take longer to stop
The condition of the brakes - worn or faulty brakes won’t stop with as much force
The amount of friction between your types and the road - you’re more likely to skid if the road is dirty, icy, wet or if the tires are bald.


What is the equation for work done by the brakes?

Energy in the car’s kinetic energy store=work done by the brakes
1/2 X car mass X velocity sq=braking force X braking distance
1/2m(v)^2 = Fd


Name the 8 energy stores and give a small explanation of each of them

Kinetic - anything moving has a kinetic energy store
Thermal - any object (the hotter it is, the more energy in this store)
Chemical - anything that can release energy through a chemical reaction
Gravitational Potential - anything in a gravitational field (it can fall)
Elastic Potential - anything stretched (strings, rubber bands)
Electrostatic - e.g. two charges that attract or repel each other
Magnetic - e.g. two magnets that attract or repel each other
Nuclear - atomic nuclei release energy from this store in nuclear reaction


Give the equation for Kinetic Energy

kinetic energy (J) = 0.5 X mass (kg) X (speed)^2 (m/s^2)
KE = 1/2 X m X v^2


What is the equation for Gravitational Potential Energy?

Gravitational Potential Energy = mass X gravitational field strength X height
GPE = m X g X h


What is Conservation of Energy

Energy can be stored, transferred between stores and dissipated but. Never created or destroyed. The total energy of a closed system has no net charge


Name the four main ways that energy is transferred between stores

Mechanically - a force acting upon an object (and doing work)
Electrically - a charge dong work
By heating - Energy transferred from a hotter object to a colder one
By radiation - energy transferred by waves


When is energy useful?

Energy is only useful when it is transferred from one store to a useful store.


What is the equation for efficiency?

Efficiency = useful transfer out / total transfer to

(X by 100 is you want a percentage)


What is the name for an efficiency diagram what is special about it?

Sankey diagram
The thickness of the arrows is in proportion (how much energy is useful/wasted)


Name the two main ways that you can reduce the amount of energy wasted

Lubrication and thermal insulation


What does friction do?

Transfers energy mechanically (work is done against the friction) to the thermal energy store of the objects involved which is then dissipated by heating to the surrounding area


What do lubricants do?

Reduce the friction between objects’ surfaces when they move. They are usually liquids (like oil) so that they can flow easily between objects and coat them


What is conduction?

When one side of an object is heated, the particles in the hotter part vibrate more and collide with each other. This transfers energy from their kinetic energy stores to other particles which then vibrate faster.


What is thermal conductivity?

A description of how well a material transfers energy by conduction. E.g. metals have a high thermal conductivity but gases have a low thermal conductivity


In a building, what does a lower thermal conductivity of its walls mean?
Some houses have cavity walls (an inner and an outer wall with an air gap in the middle). What does this do?
How might having thicker walls help?

A slower rate of energy transfer through them (meaning the building will cool more slowly)
The air gap reduces the amount of energy transferred by conduction, because air has very low thermal conductivity
The thicker the wall, the slower the rate of energy transfer


What are the two type of energy resources?

Renewable and non-renewable


What are the 11 types of energy resource?

Non-renewable: nuclear, coal, gas, oil
Renewable: hydroelectric, tidal, wave, geothermal, solar, wind, biomass


How do fossil fuel and biomass power stations work?

The fuel goes into the furnace underneath a boiler
The chimney stack allows fumes to escape from the furnace
The fuel gets burnt thereby heating the water which produces steam
The steam turns a turbine
The turbine flows to a generator - electricity out - and a cooling tower
The cooling tower condenses most of the steam into water although some escapes.


How do nuclear power stations work?

Just like fossil fuel and biomass power stations but without the burning. Instead, they react uranium or plutonium fuel which can split the atom in two. Since there are lots of uranium or plutonium atoms in the core, it becomes very hot. This then boils the water etc.


How do geothermal power stations work?

Works like fossil fuel and biomass power stations but doesn’t involve burning. Instead, they pump water down through a pipe and it is heated by the Earth. It. Is then put through a turbine etc.


How do hydroelectric power stations work?

Water flows directly through the turbines in a dam which lead directly to generators


How do wind power stations work?

Uses wind to directly turn the turbines which lead to generators


How do solar power stations work?

No turbines - the Sun’s rays shine directly onto the silicon which allows the free electrons to collide and generate electricity


How do tidal barrage power stations work?

Tidal barrages are big dams built across river estuaries with turbines in them. As the tide comes in, it fills the estuary. The water is then let out through the turbines at a controlled speed to generate electricity.


How is most of the UK’s energy produced?

Through fossil fuels and nuclear power. We do use renewable energy resources to produce some of our energy though


How has the effect on the environment caused the UK to use more renewable energy resources?

We now know that burning fossil fuels has lots of negative effects on the environment. Many people now want to use renewable energy resources which have less of an effect on the environment
Pressure from other countries and the public has meant that governments have introduced targets for usage. This puts pressure on energy providers to use renewable so that they don’t lose business and money.
Electric cars and hybrids are on the market to reduce fuel emissions


How is the the use of renewables limited to reliability and money?

Building new power plants cost money
There are lots of arguments over where they should be placed e.g. people don’t want to live next to a wind farm
Some resources aren’t as reliable as traditional fossil fuels whilst others can’t increase their power output on demand. This means either having to use a combination of different power plants or researching ways to make it more reliable - both cost money.
Making personal changes can be more expensive e.g. hybrid cars are generally more expensive than equivalent petrol cars and solar panels are quite expensive.