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Speed How to calculate average speed How speed cameras are used to measure speed Calculate speed using a known time and distance

Calculating average speed Average speed is calculated using this equation: d s x t formula triangle total distance total time average speed = Speed can be measured in different units, e.g. m/s, km/h, km/s, miles per hour. The units of distance and time used will give the units to be used for speed. How to calculate average speed Distance, speed, time, units

d s x t Speed calculation example A boy takes 1 hour to travel from his home to the cinema, a distance of 10 km. Calculate his average speed in km/h. d s x t d (distance in km) average speed (in km/h) t (time in h) = 10 km 1 h = = 10 km/h Cover the quantity to be calculated - s (speed) How to calculate average speed Distance, speed, time, units

d s x t Speed calculation example – units check d (distance in m) Sometimes the units have to be changed in a speed calculation. Here is the same problem but with different units: A boy takes 1 hour to travel from his home to the cinema, a distance of 10 km. Calculate his average speed in m/s. d s x t d (distance in m) average speed (in m/s) t (time in s) = 3600 s 10,000 m = 1x60x60 = 2.8 m/s Cover the quantity to be calculated - s (speed) How to calculate average speed Distance, speed, time, units

Question 1 A group set off from home and walk at an average speed of 3.6 km/h. How far would they travel in two hours? Give your answer in km. d s x t distance (km) = speed (km/h) x time (h) = 3.6 km/h x 2 h = 7.2 km

Distance – Time graphs How to draw and interpret distance-time graphs That the gradient of a distance-time graph represents speed Calculate the speed of an object from a graph

Which graph matches which description? Libby James: Nasir Karen Mike

Distance Time

That the gradient of a distance-time graph represents speed Difference in distance Difference in time Gradient (speed) = That the gradient of a distance-time graph represents speed Distance, speed, time, units

Acceleration and Velocity How to calculate the acceleration of an object The difference between speed and velocity Calculate relative velocity

Recap Laura covers 2000m in 1,000 seconds. What is her speed? How long would it take to run 100 metres if you run at 10m/s? Steve travels at 50m/s for 20s. How far does he go? S = D/T = 2000m/1000s = 2 m/s T = D/S = 100m/10m/s = 10s D = S x T = 50m/s x 20s = 1000m

This car is travelling at a speed of 20m/s Speed vs. Velocity Speed is simply how fast you are travelling… This car is travelling at a speed of 20m/s Velocity is “speed in a given direction”… This car is travelling at a velocity of 20m/s east The difference between speed and velocity Speed, velocity, acceleration

T A Acceleration Acceleration = change in velocity (in m/s) (in m/s2) time taken (in s) E.g: A Bugatti Veyron can do from 0 – 1609.36m in 25.9 seconds What is it’s acceleration? Acceleration = 1609.36 m = 62.14m/s2 25.9 s How to calculate the acceleration of an object Speed, velocity, acceleration

Force and Motion the effects force can have on an object How forces change the motion of objects Use the equation force=mass x acceleration

Stopping Distances What a stopping distance is The affects of stopping distance Plot graphs to represent stopping distance

Stopping Distance Thinking Distance Braking Distance The time needed for the driver to react to seeing something. Thinking Distance The total distance the car travels after the brakes have been applied Braking Distance The total distance needed to stop a car, including reaction time. What a stopping distance is Stopping, thinking, breaking distance

What a stopping distance is https://www.youtube.com/watch?v=KGkKDaYd3Mo What a stopping distance is Stopping, thinking, breaking distance

Questions The affects of stopping distance What factors can affect the thinking distance? What factors can affect braking distance? The factors that can affect thinking distance are; how tired you are, if you have used drugs or alcohol, distractions including music, sat navs or other passengers. The factors that can affect braking distance are; the speed of the car, how good the brakes are and road conditions. The affects of stopping distance Stopping, thinking, breaking distance

Work and Power What the term ‘work done’ means Work done is the same as energy transferred Use equations to calculate work and power

Work Done = force x distance (J) (N) (m) Work is done when a force moves. People and machines do work. When a person lifts a mass or pushes a shopping trolley work is done. The more massive the object lifted or the heavier the shopping in a trolley, the more work is done because a larger force is being moved. When the object or the trolley is moved a larger distance more work is done. What the term ‘work done’ means Work, power, watt, joules

Power Power = work done (J) (W) time (s) Power is how quickly work is done. If a machine does a lot of work in a short space of time it has a high power. It is measured in joules per second which scientists called watts (W). A large amount of power is measured in kilowatts (kW). 1kW = 1000W Use equations to calculate work and power Work, power, watt, joules

Work Done = force x distance (J) (N) (m) Power = work done (J) (W) time (s) Use equations to calculate work and power Work, power, watt, joules

Work Done = force x distance (J) (N) (m) Power = work done (J) (W) time (s) W D F W T P Use equations to calculate work and power Work, power, watt, joules

Kinetic Energy and Fuelling Vehicles The factors which affect kinetic energy How electricity can be used to power vehicles Discuss the advantges and disadveantages of electric vehicles

Kinetic energy = ½ x mass x speed2 Any moving object has energy due to its motion. This is its kinetic energy. Any moving object has kinetic energy. If an object is not moving, it has zero kinetic energy. The size of an object’s kinetic energy depends on the mass of the object and the speed at which it is travelling. Kinetic energy = ½ x mass x speed2 (joules, J) (Kilograms, kg) (metres per second, m/s)2 The factors which affect kinetic energy Kinetic energy, fuel consumption, fossil fuel

Kinetic Energy Kinetic energy = ½ x mass x speed2 (joules, J) (Kilograms, kg) (metres per second, m/s)2 1) Find the kinetic energy of a car of mass 1200kg travelling at 20m/s. Kinetic energy = ½ x 1200kg x (20m/s)2 = ½ x 1200 x 400 = 240000J or 240kJ The factors which affect kinetic energy Kinetic energy, fuel consumption, fossil fuel

Fuelling Vehicles Read pages 184 and 185 of your textbook and answer the following exam questions. (write the question and answer) Explain what it means when we say that electric cars don’t produce pollution at their point of use. (2 marks) State and explain 3 factors which affect fuel consumption of a typical car. (3 marks) Outline the advantages and disadvantages of using electric cars over conventional fossil fuel powered cars. (6 marks QWC) https://www.youtube.com/watch?v=s0seCNxRUmI How electricity can be used to power vehicles Kinetic energy, fuel consumption, fossil fuel

Extended writing question Outline in detail two advantages and two disadvantages of using biofuels to generate electricity. How will you structure your answer? What is the question asking you? What keywords should you include? Describe the advantages and disadvantages of using fossil fuels and biomass Biofuel, biomass, fossil fuel

Collisions and Car Safety The safety features of cars The effectiveness of safety features Calculate momentum

Collapsible steering column Safety Features Paddle control seatbelt airbag Crumple zone Electric windows Collapsible steering column Traction control ABS The safety features of cars Momentum, crumple zone, ABS

momentum = mass x velocity Force (N) = change in momentum (kg m/s) During a collision a quantity called momentum is conserved. When the car slows down during impact its momentum decreases. As it decreases, the passengers feel a force which can result in injury, e.g. whiplash. You can calculate momentum using this equation: The force experienced by a passenger during a collision depends upon the rate of changes of momentum. The quicker the change in momentum, the greater the force experienced. You can calculate the force using the following equation: momentum = mass x velocity Force (N) = change in momentum (kg m/s) time taken (s) The safety features of cars Calculate momentum

6 Mark Question The safety features of cars Calculate momentum

Falling objects and drag How to calculate the weight of an object The motion of an object falling under gravity Explain that drag increases with speed

Terminal Speed When a skydiver jumps out of an aeroplane, the speed of their descent can be considered in two separate parts: Before the parachute opens (when the skydiver is in free-fall). After the parachute opens (when air resistance is greatly increased). The motion of an object falling under gravity Weight, gravitational field strength, drag

Weight and Mass Weight is due to the force of gravity of an object. The mass of an object is the amount of matter that it contains. Weight and mass are linked by two related formulae: Weight (N) = Mass (kg) x Acceleration or free-fall (m/s²) or Gravitational field strength (N/kg) How to calculate the weight of an object Weight, gravitational field strength, drag

Gravitational field strength or acceleration due to gravity: is unaffected by atmospheric changes varies slightly at different points on the Earth’s surface will be slightly different on the top of a mountain or down a mineshaft.

Gravitational potential energy What factors affect GPE The energy changes taking place as an object falls Calculate GPE using an equation

The Conservation of Energy Energy cannot be created or destroyed. It is converted into different forms. For a roller coaster, energy is transformed between gravitational potential and kinetic energy. The principle of conservation of energy tells us that gravitational potential energy (GPE) at the top of a roller coaster = kinetic energy (KE) at the bottom + energy transferred as heat and sound.

Gravitational Potential Energy The gravitational potential energy (GPE) of an object is the energy stored due to: its position in the Earth’s gravitational field (height) its mass. You can calculate GPE using this formula: mass x gravitational field strength x vertical height (kg) (N/kg) (m)

Fairground Rides At the peaks on the ride the train has a lot of GPE (high up) and little KE (moves slowly). In the middle of the ride GPE is decreasing and KE is increasing. The more GPE gained by the train on the roller coaster, the greater it’s maximum speed. At the bottom the train has little GPE (low down) but a lot of KE (moves fast).