P2 topic 4

Question 1

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

Answer 1

thinking distance and braking distance

Question 2

thinking distance

Answer 2

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

Question 3

braking distance

Answer 3

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

Question 4

how can thinking distance be calculated?

Answer 4

speed of car x reaction time

Question 5

how can stopping distance be calculated?

Answer 5

thinking distance + braking distance

Question 6

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

Answer 6

the car continues to move at a constant speed

Question 7

what increases the thinking distance?

Answer 7

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

Question 8

when does the driver’s reaction time increase?

Answer 8

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

Question 9

when does the braking distance increase?

Answer 9

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

Question 10

when else does braking distance increase?

Answer 10

when there is reduced friction

Question 11

how is friction reduced?

Answer 11

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

Question 12

why is friction a nuisance?

Answer 12

it wastes energy

Question 13

why is friction useful?

Answer 13

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

Question 14

how can you reduce the friction between two surfaces?

Answer 14

lubricating them

Question 15

how can total stopping distance be shown?

Answer 15

on a velocity-time graph

Question 16

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

Answer 16

it’s equal to the distance travelled

Question 17

what do cars rely on to stop?

Answer 17

friction, created using their brakes

Question 18

when will the momentum of an object be big?

Answer 18

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

Question 19

principle of conservation of momentum

Answer 19

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

Question 20

how can the impact force on an object be reduced?

Answer 20

by increasing the time taken for the object to stop

Question 21

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

Answer 21

seat belts, crumple zones and air bags

Question 22

seat belts

Answer 22

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

Question 23

crumple zones

Answer 23

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

Question 24

air bags

Answer 24

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

Question 25

what do all moving objects have?

Answer 25

kinetic energy

Question 26

what is an object's kinetic energy determined by?

Answer 26

mass and speed

Question 27

what is KE measured in?

Answer 27

joules

Question 28

standard measurement for mass

Answer 28

kg

Question 29

what is potential energy?

Answer 29

stored energy

Question 30

principle of conservation of energy

Answer 30

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

Question 31

what is KE transferred to when a cyclist brakes?

Answer 31

heat in the brakes and sound

Question 32

what is the energy transfer in a petrol car?

Answer 32

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

Question 33

what is the energy transfer of a parachutist falling?

Answer 33

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

Question 34

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

Answer 34

GPE is converted to KE

Question 35

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

Answer 35

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

Question 36

when is there work done?

Answer 36

when a force is applied to an object and it moves

Question 37

what is work done measured in?

Answer 37

Newton metres or joules

Question 38

what is 1 joule?

Answer 38

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

Question 39

power

Answer 39

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

Question 40

what is 1 watt equal to?

Answer 40

1 joule per second

Question 41

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

Answer 41

if the car is travelling at a constant velocity

Question 42

what do all moving objects have?

Answer 42

momentum

Question 43

what does a minus sign imply?

Answer 43

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

Question 44

principle of conservation momentum

Answer 44

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

Question 45

what happens when objects travelling in different directions collide?

Answer 45

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

Question 46

what is an object's kinetic energy determined by?

Answer 46

its mass and speed/velocity

Question 47

what is work done by a force equal to?

Answer 47

energy transferred

Question 48

what is 1 watt equal to?

Answer 48

1 joule per second