P10

What does Newton's second law of motion say?
Proportional to the resultant force on the object, inversely proportional to mass of object
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What is inertia?
The tendency of an object to stay at rest or to continue in uniform motion
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What is needed to change the velocity of an object?
A resultant force
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What happens if the velocity of an object changes?
It must be acted on by a resultant force
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What happens if the velocity of an object increases?
Resultant force in same direction as velocity, acceleration is positive
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What happens if the velocity of an object decreases?
If resultant force in opposite you say acceleration is negative
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What is weight?
Force acting on it due to gravity
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What is mass?
Quantity of matter in it
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What happens if an object falls in fluid?
The fluid drags on the object because of fluid between fluid and object
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Why does the acceleration of an object decrease as it falls?
Frictional force increases as it speeds up so resultant force decreases and so does acceleration
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When does an object reach a constant velocity?
When frictional force on it is equal and opposite to its weight
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What is that velocity called?
Terminal velocity- when resultant = 0 and acceleration = 0
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What does braking force of a vehicle depend on?
Speed of car and mass of car
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What is the relationship between speed and braking force?
Higher the speed higher the braking force same with mass of car
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What is stopping distance?
Shortest distance a vehicle can safely stop in
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What is thinking distance?
The distance travelled by the vehicle in time for driver to react
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What is braking distance?
Distance travelled by vehicle during time braking force acts
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What is the formula for stopping distance?
Thinking distance + braking distance
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What is the equation for deceleration?
Same as acceleration but with a -
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What affect reaction times which effects stopping distance?
Tiredness, drugs, alcohol and mobile phones
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How does weather affect stopping distance?
Icy and slippy roads cause braking with less force
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How does poorly maintained vehicles affect stopping distance?
Can take longer to break as is less effective
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What is the law of conservation of momentum?
In a closed system the total momentum before an event is equal to the total momentum after
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What happens if an impact time is longer?
The more the impact force is reduced
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What happens when two vehicles collide?
They exert equal and opposite forces and their total momentum is unchanged
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What is the equation for impact force?
Change of momentum/ impact time
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What is the point in a helmet?
It increases impact time
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What is the point of a seatbelt?
It decreases decelerating force
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Why does the seatbelt go across the chest?
It spreads force out
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What do airbags do?
Spread force of impact across upper part of body, increases impact time
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What is a crumple zone?
The structural safety feature that absorbs energy
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What is the point of cushioned surfaces?
They increase impact time and impact force reduced
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How to know if an object is elastic?
It returns to original shape when force deforming it is removed
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What is Hookes law?
The extension of a spring is directly proportional to the force applied
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Other cards in this set

Card 2

Front

What is inertia?

Back

The tendency of an object to stay at rest or to continue in uniform motion

Card 3

Front

What is needed to change the velocity of an object?

Back

Preview of the front of card 3

Card 4

Front

What happens if the velocity of an object changes?

Back

Preview of the front of card 4

Card 5

Front

What happens if the velocity of an object increases?

Back

Preview of the front of card 5
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