Chapter 1 - Motion, Forces and Conservation of Energy

Question 1

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

Answer 1

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

Question 2

What is displacement?

Answer 2

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

Question 3

What can you measure a vector direction as?

Answer 3

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

Question 4

What is the equation for speed (m/s)

Answer 4

Distance travelled (m)/Time (s)

Question 5

What is uniform acceleration?

Answer 5

Accelerating/decelerating at a constant rate

Question 6

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

Answer 6

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

Question 7

What is the equation for uniform acceleration?

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

What is Newton’s First Law?

Answer 12

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.

Question 13

What is Newton’s Second Law?

Answer 13

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

Question 14

What is Newton’s Third Law?

Answer 14

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

Question 15

What is the difference between weight and mass?

Answer 15

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).

Question 16

What is the equation for weight?

Answer 16

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

Question 17

What is centripetal force?

Answer 17

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.

Question 18

What is inertia?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is the equation for momentum

Answer 20

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

Question 21

Is momentum a scalar or a vector quantity?

Answer 21

Vector - always include a direction

Question 22

What is the Conservation of Momentum?

Answer 22

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

Question 23

What is the equation for change in momentum?

Answer 23

F=(mv-mu)/t

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

Question 24

What is the stopping distance of a car?

Answer 24

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

Question 25

What is thinking distance and what might affect it?

Answer 25

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

Question 26

What is the braking distance and what might affect it?

Answer 26

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.

Question 27

What is the equation for work done by the brakes?

Answer 27

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

Question 28

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

Answer 28

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

Question 29

Give the equation for Kinetic Energy

Answer 29

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

Question 30

What is the equation for Gravitational Potential Energy?

Answer 30

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

Question 31

What is Conservation of Energy

Answer 31

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

Question 32

Name the four main ways that energy is transferred between stores

Answer 32

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

Question 33

When is energy useful?

Answer 33

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

Question 34

What is the equation for efficiency?

Answer 34

Efficiency = useful transfer out / total transfer to | X by 100 is you want a percentage

Question 35

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

Answer 35

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

Question 36

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

Answer 36

Lubrication and thermal insulation

Question 37

What does friction do?

Answer 37

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

Question 38

What do lubricants do?

Answer 38

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

Question 39

What is conduction?

Answer 39

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.

Question 40

What is thermal conductivity?

Answer 40

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

Question 41

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?

Answer 41

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

Question 42

What are the two type of energy resources?

Answer 42

Renewable and non-renewable

Question 43

What are the 11 types of energy resource?

Answer 43

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

Question 44

How do fossil fuel and biomass power stations work?

Answer 44

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.

Question 45

How do nuclear power stations work?

Answer 45

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.

Question 46

How do geothermal power stations work?

Answer 46

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.

Question 47

How do hydroelectric power stations work?

Answer 47

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

Question 48

How do wind power stations work?

Answer 48

Uses wind to directly turn the turbines which lead to generators

Question 49

How do solar power stations work?

Answer 49

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

Question 50

How do tidal barrage power stations work?

Answer 50

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.

Question 51

How is most of the UK’s energy produced?

Answer 51

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

Question 52

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

Answer 52

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

Question 53

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

Answer 53

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.