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Physics > P2 topic 4 > Flashcards

P2 topic 4 Flashcards

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1
Q

what is the stopping distance of a car made up of?

A

thinking distance and braking distance

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2
Q

thinking distance

A

the distance travelled by the car as the driver reacts to apply the brakes

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3
Q

braking distance

A

the distance travelled by the car whilst the brakes are applied before the car comes to a halt

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4
Q

how can thinking distance be calculated?

A

speed of car x reaction time

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5
Q

how can stopping distance be calculated?

A

thinking distance + braking distance

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6
Q

what happens to the speed of the car during the thinking distance?

A

the car continues to move at a constant speed

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7
Q

what increases the thinking distance?

A

the speed of the car increasing, the driver’a reaction time increasing

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8
Q

when does the driver’s reaction time increase?

A

when he/she is tired, is under the influence of drugs or alcohol, is distracted (eg by passengers or mobile phones)

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9
Q

when does the braking distance increase?

A

when the mass of the car increases, when the speed of the car increases

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10
Q

when else does braking distance increase?

A

when there is reduced friction

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11
Q

how is friction reduced?

A

it’s reduced between the tyres and roads because of work tyres, between tyres and road because of wet/icy road surface, because of worn brakes

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12
Q

why is friction a nuisance?

A

it wastes energy

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13
Q

why is friction useful?

A

it helps us to walk and it also helps vehicles to slow down

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14
Q

how can you reduce the friction between two surfaces?

A

lubricating them

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15
Q

how can total stopping distance be shown?

A

on a velocity-time graph

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16
Q

what does the area under a velocity-time graph show?

A

it’s equal to the distance travelled

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17
Q

what do cars rely on to stop?

A

friction, created using their brakes

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18
Q

when will the momentum of an object be big?

A

if the object is travelling quickly and it has a large mass

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19
Q

principle of conservation of momentum

A

for a system of colliding objects, where there are no external forces, the total momentum before and after the collision remains the sea

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20
Q

how can the impact force on an object be reduced?

A

by increasing the time taken for the object to stop

21
Q

what features are there in a car to help reduce the rate of change of momentum on the passengers?

A

seat belts, crumple zones and air bags

22
Q

seat belts

A

stretch slightly during a crash- this increases the time taken for the passenger to stop, reducing impact force to a safe level

23
Q

crumple zones

A

cars are designed to crumple- the car, and hence the driver, takes a longer time to stop, reducing the impact force on the driver

24
Q

air bags

A

they inflate suddenly during a collision- the stopping time is longer and the impact force on the driver is reduced

25
Q

what do all moving objects have?

A

kinetic energy

26
Q

what is an object’s kinetic energy determined by?

A

mass and speed

27
Q

what is KE measured in?

A

joules

28
Q

standard measurement for mass

A

kg

29
Q

what is potential energy?

A

stored energy

30
Q

principle of conservation of energy

A

energy cannot be created or destroyed, it can simply be transferred from one form to another

31
Q

what is KE transferred to when a cyclist brakes?

A

heat in the brakes and sound

32
Q

what is the energy transfer in a petrol car?

A

chemical energy of the fuel is changed into KE, heat and sound

33
Q

what is the energy transfer of a parachutist falling?

A

their GPE is transformed to KE, hear and a little bit of sound

34
Q

what is their GPE transferred to as a diver falls off a diving board?

A

GPE is converted to KE

35
Q

what does it mean if the braking force and mass of a car are constants?

A

braking distance is directly proportional to velocity squared- doubling the velocity of the car quadruples the braking distance

36
Q

when is there work done?

A

when a force is applied to an object and it moves

37
Q

what is work done measured in?

A

Newton metres or joules

38
Q

what is 1 joule?

A

the work done when a force of 1 Newton moves through a distance of 1m in the direction of the force

39
Q

power

A

the rate at which work is done, or that rate at which energy is transferred

40
Q

what is 1 watt equal to?

A

1 joule per second

41
Q

When is the only time that the equation P=Fv will work?

A

if the car is travelling at a constant velocity

42
Q

what do all moving objects have?

A

momentum

43
Q

what does a minus sign imply?

A

an object is moving in the opposite direction- momentum is a vector quantity

44
Q

principle of conservation momentum

A

for a system of colliding objects, when there are no external forces, the total momentum before and after the collision remains the same

45
Q

what happens when objects travelling in different directions collide?

A

the vector nature of movement before and after a collision must be taken into account

46
Q

what is an object’s kinetic energy determined by?

A

its mass and speed/velocity

47
Q

what is work done by a force equal to?

A

energy transferred

48
Q

what is 1 watt equal to?

A

1 joule per second

Physics (15 decks)

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