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Flashcards in P3 1-8 Deck (13):

How do speed cameras work?

Some speed cameras are used together with lines painted on the road. As the car passes over the lines the camera takes two pictures 0.2 seconds apart. The distance travelled by the vehicle in that time is found by looking at the two photos. So the distance and time are known. The speed can then be calculated.


How do average speed cameras work?

Average speed cameras use a pair of cameras to work out the average speed of a car. The cameras read the car’s number plate and record the time when the car passes each camera. The distance between the two cameras is known, so the car’s speed can be worked out using the average speed equation.


How can you tell how fast something is on a distance time graph?

The gradient. If the car is moving faster, it goes a greater distance in every 50 seconds and the slope of the line is steeper. If the car is slower, it moves a smaller distance every 50 seconds and the slope is less steep.


What do positive and negative gradients mean on a distance time graph?

The distance on a distance–time graph means the distance from a particular point. When an object is moving away from the fixed point, the graph slopes upwards to the right – it has a positive gradient. When the object is moving back towards the fixed point, the graph slopes downward to the right – the gradient is negative.


What is acceleration and deceleration?

A moving object might speed up or slow down. This change in speed is called acceleration.When something is slowing down, it will have a negative acceleration. In everyday language, negative acceleration is called deceleration.


What is velocity?

Velocity tells you the direction an object is travelling in as well as its speed.


What is relative velocity?

A car is moving at +70 mph, and a train is moving in the same direction at +80 mph. For the people in the car, the train is travelling past them at 80 – 70 mph, that is 10 mph. The difference in velocity, called the relative velocity, is 10 mph.


How can you find distance in a speed time graph?

The area under the speed time graph line


What is resultant force?

the sum of all the forces acting on an object, taking their directions into account.


What is stopping distance?

Thinking distance + braking distance


What can affect thinking distance?

- Fatigue
- Drugs e.g alcohol or marijuana
- prescription drugs
- Distractions e.g music, mobile phones or satellite navigation system, or even talking to passengers can increase reaction time.
- Age
- Speed


What can affect braking distance?

- speed
- Worn brakes
- too much force is applied, the wheels can lock and the car skids.
- Road conditions e.g road surface is icy or wet there is less friction between the tyres and the road and the tyres may slip.
- worn tires


What is work done and power?

Work done - energy transferred
Power - work done in a certain time