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Why might people take risk? familiarity, adrenaline rush,
Define acceleration (change in velocity)/the time taken = (v-u)/t
What 2 properties does a vector quantity have? magnitude ( size) and direction
How do you calculate the acceleration from a velocity time graph? the gradient of the graph
If the resultant force acting on a body is not zero, what will it do? accelerate in the direction of the force
What are the 2 possible actions that a body could have if the resultant force on it is zero? constant velocity or remain stationary
What is the relationship between force mass and acceleration? F=mxa
What is Newtons third law? When two bodies interact, the forces they exert on each other are equal in size and opposite in direction and that these are known as action and reaction forces
What 2 forces act on a falling object? Falling objects are acted on by a downward force (weight) and an upward force (air resistance) and that at the start of the fall the forces are unbalanced and the object accelerates
What happens to the air resistance as the the speed of an object falling through it increases? the increase in resistance with an increase in speed for a falling object
When does terminal velocity occur? When weight downwards = air resistance upwards
What is stopping distance? Total distance travelled between seeing reason to stop and stopping. Stopping distance =thinking distance + braking distance
What is thinking distance? Distance travelled between seeing reason to stop and foot touching brake. Thinking distance = speed x reaction time
What is braking distance? Distance travelled from time foot hot brakes to when the car stops.
What factors increase thinking distance? Driver drinking, drugs, mobile phone use. Anything that increases the reaction time
What factors increase braking distance? poor brakes, worn tyres, ice, wet weather, anything that reduces friction between road and tyre
What methods can be used to express risk? Fractions, ratios and percentages
What is the difference between imposed risk and voluntary risk? Imposed - no choice e.g. going to school on bus. Voluntary risk- a choice e.g. skiing, crossing the road not at a zebra crossing.
Describe and explain measures designed to reduce the rate of change of momentum of fragile objects, eg passengers on a rollercoaster Change of momentum acts over a larger time reducing the impact time. So brakes are applied gradually. Accelerating and decelerating forces are calculated to ensure that they will not injure the passenger.
How can we express force in terms of momentum change? Force= the rate of change of momentum F= (mv-mu)/t mv = final momentum mu = initial momentum
Explain how seat belts and air bags work? Increase the time to decelerate, momentum changes more slowly , reducing the force on the passenger. They stop the passengers hitting windscreen and dashboard.
How do crumple zones work? The car crumples and absorbs the energy more slowly in the collision. Increasing the collision time, reducing the collision force (rate of change of momentum is reduced).
What is the formula for momentum? Mass x velocity
What is the unit of momentum? kg m/s
What is the units of force? newtons
What is a unit of acceleration m/s/s
What does the symbol v stand for? Final velocity
What does the symbol u stand for? initial velocity
Name some computer simulation programmes that would use real force data in order to model ' what if' situations Flight simulators, car design
Created by: Susan E Casey
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