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Flashcards in P2a Deck (51):
1

Speed

How fast you are going without direction

2

Velocity

How fast you are going with direction

3

Speed=

Distance/time

4

Acceleration

How quickly a velocity is changing

5

Resultant force

The overall force on a point or object

6

An object needs...

A force to start moving

7

No resultant force means...

No change in velocity

8

A resultant force means...

Acceleration

9

Reaction forces are...

Equal and opposite- when two objects interact, the forces they exert on each other are equal and opposite

10

Friction is always there to...

Slow things down

11

Friction acts in the...

Opposite direction to movememt

12

Drag...

Increases as the speed increases- the faster your going the more drag you have

13

Terminal velocity

When an object falls, the gravity is much greater than the frictional force - this leads to acceleration

As the speed increases, the friction builds up
This reduces the acceleration until eventually the frictional force is equal to the accelerating force - it remains at a steady maximum speed

14

Stopping distance

Breaking distance + thinking distance

15

Thinking distance

The distance the vehicle travels during the drivers reaction time

16

Thinking distance can be affected by...

How fast your going
How tired you are
Whether you have had alcohol or drugs
Bad visibility
Distractions
Hazards

17

Braking distance

The distance the vehicle travels under the braking force

18

Breaking distance can be affected by...

How fast your going
How good your tires are
How good your breaks are
How good the grip is - road surface, weather conditions and tires

19

Work done definition

When a force moves an object through a distance, energy is transferred and work is done

20

Gravitational potential energy

Energy due to height
Measured in joules

21

Kinetic energy

Energy of movement

22

Kinetic energy depends on...

The speed and mass of an object

23

When a car is stopping...

The kinetic energy is converted into heat energy as friction between the wheels and the break pads, causing the temperature to increase

24

Falling objects...

Convert their potential energy into kinetic energy


Kinetic energy gained= potential energy lost

25

Forces causes change in momentum

When a force acts on an object, it causes a change in momentum

A larger force means a faster change in momentum

Likewise - if someone's momentum changes very quickly, the force on the body will be very large

26

Electric or hybrid cars have...

Regenerating braking system

27

Regenerating braking system

Break puts vehicles motor into reverse. This means wheels slow down
At the same time the motor acts as an electrical generator, converting kinetic energy into electrical energy that is then stored as chemical energy in the vehicles battery

28

Cars are designed to convert kinetic energy safely in a crash

In a crash, there is a big change in momentum over a short amount of time, this means people in the car experience a large amount of force that could be fatal

29

Cars are designed to...

Convert the kinetic energy of the car in a safe way. They do this by increasing the time over which momentum changes happen, therefore reducing the force felt on the person

30

Crumple zone

Kinetic energy is converted into other forms of energy by the car body as it changes shape

Increases the impact time, decreasing the force produced by the change in momentum

31

Side impact bars

Strong metals bars in the car door panel- this directs the kinetic energy away from the passenger

32

Seat belt

Increases the time taken for the change in momentum, reducing the force acting on the chest

Some kinetic energy is absorbed by the seat belt stretching

33

Air bags

Allows you to slow down more gradually- less force due to a slower change in momentum

Also prevents you from hitting hard surfaces inside the car - soft landing

34

Static electricity build up

Build up of static electricity is caused by friction

35

How static electricity works

When certain insulating materials rub together, negatively charged electrons will be scraped off and dumped on the other

This leaves a positive static charge on one and a negative static charge on the other

Electrically charged objects attract small objects placed near them

36

Current

Is the flow of electric charge round the circuit, current will only flow through a component if there is a potential difference across the component

Unit - Ampere, A

37

Potential difference/ voltage

The difference in energy carried by an electrical charge between two points in a circuit. It's also the driving force that pushes the current around

Units - Volts, V

38

Resistance

Anything in the circuit which slows the flow down

Unit - Ohms

40

The bigger the potential difference...

The higher the current.

This is because the current flows from a high energy point to a low energy point

41

The ammeter

Must be placed in the series
Can be placed anywhere in the series
Measures the currents flowing through the component

42

The voltmeter

Measures potential difference across the component
Must be placed in parallel around the component under the test

43

Varying the resistor...

Alters the current flowing through the circuit

44

Different resistor graph

The current through a resistor is directly proportional to the potential difference

45

Diode graph

Current will only flow through a diode in one direction

46

LED

Emits light when a current is flowing through it in a forward direction
They work with a much smaller current than filament bulbs

47

Diode

It's used to regulate the potential difference in a circuit
Only let's current flow in one direction

48

LDR

A light sensitive resistor

In bright lights the resistance falls
In darkness the resistance is highest

49

Thermistor

Heat sensitive resistor

In hot conditions the resistance falls
In cool temperatures the resistance is highest

50

Series circuit rules

Potential difference is shared
Current is the same everywhere
Resistance adds up
Cell voltages add up

51

Parallel circuit rules

Potential difference is the same across all components
Current is shared between branches

52

Filament lamp graph

As the temperature increases, the resistance increases