P3 Spaced learning

Forces for transport

SpeedSpeed = Average Distance/TimeKM x 1000 = MM / 1000 = KM

AverageSpeed CamerasTakes two photos, a certain time apart, when the vehicle moves over marked lines a know distance apart.

Graphs – distance / time graphs, how the distance changes over time.Gradient (steepness) = speed (steeper faster)Steady speed – straight diagonal line (up or down)Stationary – horizontal line

• increasing the speed, increases thedistance travelled in the same time• increasing the speed, reduces the time to cover the same distance.distance = average speed × time

=(u + v)/2 × td is the distanceu is the starting speedv is the finishing speedt is the time taken

You need to be able to draw one.

Non – uniform speed:Curved line upwards – accelerationCurved line downwards - decceleration

Use the unit s on the graph combined for speed

Changing speedacceleration = change in speed / time taken

A change in speed per unit of time

- metres per second squared (m/s2)- involves change in speed and/or direction

Velocity – speed and direction

You need to be able to draw one

Change in speed = end speed – start speed

Horizontal line - constant speedStraight line (positive gradient) - constant positive acceleration (speeding up)Straight line (negative gradient) - constant negative acceleration e.g. -2m/s (slowing down) or decelerationSteeper line (greater change in speed in given time)– higher accelerationCurved line –up increasing acceleration –down decreasing acceleration

Calculate distance – area under the graph (meters)

Objects moving in opposite directions at the same speed, velocities have identical magnitude but opposite signs. E.g. +30m/s and – 30m/s

Relative velocity: Velocity A – Velocity B e.g. +30 m/s - +20 m/s =+10 m/s OR +30 m/s - -20 m/s =+50 m/s

Gradient = acceleration

Forces and motion

force = mass × acceleration

Thinking distance - the distance travelled between the need for braking occurring and the brakes starting to act. Increased if: Tired, Distracted or not concentrating, Under the influence of alcohol or other drugs, increased speed, distractions or lack of concentration.Braking distance - the distance taken to stop once the brakes have been applied. Increased if: The car's brakes or tyres are in poor condition, The road and weather conditions are poor (icy or wet roads, for example)., increased speed, Friction, mass, speed, braking force.Stopping distance - thinking distance + braking distance.

Road safety - Speed limits - go no faster than safe for normal conditions. Road conditions- icy etc.‘tail gates’ –drives too close to the vehicle in front, (inside thinking distance).

Force - newtons, NMass - kilograms, kgAcceleration -metres per second squared, m/s2

Resultant force is zero - stay at the same speed.Resultant force is not zero - speed up or slow down, +ve or –ve.Speed up - resultant force is in the same direction as object is movingSlow down - resultant force is in the opposite direction

stopping distance = thinking distance + braking distance

Speed and: thinking distance – increases linearlybraking distance – increases as a squared relationship e.g. x2 x4, x3 x9.

Work and Powerweight = mass × gravitational field strengthWeight -newtons, NMass -kilograms, kgThe gravitational field strength -newtons per kilogram, N/kg

Mass - how much stuff is in an object. Weight - force acting on that stuff due to gravity.

gravitational field strength of the Moon is about one-sixth of that of the Earth

Work done = force × distanceWork done -joules, JForce - newtons, NDistance - metres, mJ also used for energyExamples• lifting weights• climbing stairs• pulling a sledge• pushing a shopping trolley.

Depends on:the size of the force in newtons (N)the distance travelled in metres (m).

Power = Work done / time How quickly work is being done. Watts (W).Cars:• have different power ratings• have different engine sizesAffecting fuel consumption – environmental issues, cost

Use and understand the derivation of the powerequation in the form:power = force × speedPower -watts, W

Work done -joules, JTime -seconds, s

Energy on the move Kinetic energy – depends on mass and speed

KE = ½ mv2orKE = ½ × m × v2

KE = the kinetic energy in joules, Jm = the mass in kilograms, kgv = the speed in metres per second, m/s

(derivatives of) fossil fuels - fuels in road transport: petrol, diesel. Will run out

kinetic energy proportional to speed squared, braking distances proportional to the speed squared. Rearrange equation for kinetic energy. m = (2 × KE) ÷ v2

v2 = (2 × KE) ÷ m

Alternatives - bio-fuels and solar energy.• reduce pollution at the point of use• produce pollution in their production• may lead to an overall reduction in CO2emissions.Electricity used for road transport, battery driven cars, solar power/cars with solar panels, do not pollute at point of use.

Affect on fuel consumption:Shape - wedge shape of sports car, deflectors on lorries and caravans, roof boxes on cars, driving with car windows open. Other factors - Driven uphill a lot, Carrying large loads or not, Driven at high speed, Driven over rough road surfaces, Driven with underinflated tyres. energy required to increase KE, energy required to do work against friction, driving styles and speeds, road conditions.

Carbon dioxide - greenhouse gas (global warming) Sulfur dioxide - cause of acid rain.

Recognise that battery driven cars need to have the battery recharged:• this uses electricity from a power station• cause pollution

Crumple zonesMomentum = mass × velocityMomentum - kilograms metres per second, kg m/sMass - kilograms, kgVelocity - metres per second, m/s

Sudden change in momentum – large force- cause injury

Force = change in momentum ÷ timeForce - newtons, NChange in momentum - kilograms metres per second, kg m/sTime - seconds, s

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Change in momentum - the longer the time taken, the smaller the force needed.

Car safety features

Risks and benifits

Falling safely

The energy of games and theme rides

Musical Chairs

SpeedSpeed = Average Distance/TimeKM x 1000 = MM / 1000 = KM

AverageSpeed CamerasTakes two photos, a certain time apart, when the vehicle moves over marked lines a know distance apart.

Graphs – distance / time graphs, how the distance changes over time.Gradient (steepness) = speed (steeper faster)Steady speed – straight diagonal line (up or down)Stationary – horizontal line

• increasing the speed, increases thedistance travelled in the same time• increasing the speed, reduces the time to cover the same distance.distance = average speed × time

=(u + v)/2 × td is the distanceu is the starting speedv is the finishing speedt is the time taken

You need to be able to draw one.

Non – uniform speed:Curved line upwards – accelerationCurved line downwards - decceleration

Use the unit s on the graph combined for speed

Changing speedacceleration = change in speed / time taken

A change in speed per unit of time

- metres per second squared (m/s2)- involves change in speed and/or direction

Velocity – speed and direction

You need to be able to draw one

Change in speed = end speed – start speed

Horizontal line - constant speedStraight line (positive gradient) - constant positive acceleration (speeding up)Straight line (negative gradient) - constant negative acceleration e.g. -2m/s (slowing down) or decelerationSteeper line (greater change in speed in given time)– higher accelerationCurved line –up increasing acceleration –down decreasing acceleration

Calculate distance – area under the graph (meters)

Objects moving in opposite directions at the same speed, velocities have identical magnitude but opposite signs. E.g. +30m/s and – 30m/s

Relative velocity: Velocity A – Velocity B e.g. +30 m/s - +20 m/s =+10 m/s OR +30 m/s - -20 m/s =+50 m/s

Gradient = acceleration

Forces and motion

force = mass × acceleration

Thinking distance - the distance travelled between the need for braking occurring and the brakes starting to act. Increased if: Tired, Distracted or not concentrating, Under the influence of alcohol or other drugs, increased speed, distractions or lack of concentration.Braking distance - the distance taken to stop once the brakes have been applied. Increased if: The car's brakes or tyres are in poor condition, The road and weather conditions are poor (icy or wet roads, for example)., increased speed, Friction, mass, speed, braking force.Stopping distance - thinking distance + braking distance.

Road safety - Speed limits - go no faster than safe for normal conditions. Road conditions- icy etc.‘tail gates’ –drives too close to the vehicle in front, (inside thinking distance).

Force - newtons, NMass - kilograms, kgAcceleration -metres per second squared, m/s2

Resultant force is zero - stay at the same speed.Resultant force is not zero - speed up or slow down, +ve or –ve.Speed up - resultant force is in the same direction as object is movingSlow down - resultant force is in the opposite direction

stopping distance = thinking distance + braking distance

Speed and: thinking distance – increases linearlybraking distance – increases as a squared relationship e.g. x2 x4, x3 x9.

Work and Powerweight = mass × gravitational field strengthWeight -newtons, NMass -kilograms, kgThe gravitational field strength -newtons per kilogram, N/kg

Mass - how much stuff is in an object. Weight - force acting on that stuff due to gravity.

gravitational field strength of the Moon is about one-sixth of that of the Earth

Work done = force × distanceWork done -joules, JForce - newtons, NDistance - metres, mJ also used for energyExamples• lifting weights• climbing stairs• pulling a sledge• pushing a shopping trolley.

Depends on:the size of the force in newtons (N)the distance travelled in metres (m).

Power = Work done / time How quickly work is being done. Watts (W).Cars:• have different power ratings• have different engine sizesAffecting fuel consumption – environmental issues, cost

Use and understand the derivation of the powerequation in the form:power = force × speedPower -watts, W

Work done -joules, JTime -seconds, s

Exam questions