Flashcards in Forces Deck (46)

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31

## What is velocity?

### It is the speed in a GIVEN DIRECTION. It is a vector quality.

32

## How do you calculate the speed of an object?

### Speed (m/s) = distance (m) / time (s)

33

## What is acceleration? Equation?

###
It is the rate of change of the velocity. It is the change in velocity in an amount of time.

Acceleration (m/s2) = v-u (m/s) / time (s)

34

## What does a distance time graph show us?

###
-gradient=speed

-flat sections=object stationary

-straight sections=steady constant speed

-levelling off=slowing down

If object is accelerating, find the gradient of tangent to the curve at that point it's speed has changed

35

## What does a velocity time graph show us?

###
How an objects velocity changes on a journey.

-gradient=acceleration

-flat sections=steady speed

-steeper the graph=greater acceleration/deceleration

-area under sections of graph equal to distance traveled in that time

36

## What is drag? How can it be avoided?

###
Resistance you get in a fluid (gas or liquid) air resistance is a type of drag. Drag increases as the speed increases.

Can be reduced by keeping shape of object streamlined eg train

37

## What does it mean if an object is in equilibrium?

### It's weight is equal to the normal contact force.

38

## What is the stopping distance?

###
The sum of the thinking distance and the breaking distance. It is the distance it takes to stop a car.

Stopping distance = thinking distance + breaking

distance

39

## What is the thinking distance? What affects this?

###
How far the car travels during the drivers reaction time. It is affected by:

-speed

-your reaction time- tiredness, drugs, alcohol, distractions

40

## What is your reaction time? What affects it?

###
The distance taken to stop once the brakes are applied. It is affected by:

-speed

-road surfaces/weather

-condition of tyres

-condition of brakes

41

## What happens when the brakes of a car are applied? Hazards?

###
-brake pads pushed onto wheels which cause friction which causes work to be done

-the work done between wheels and brakes transfers energy from kinetic energy stores to thermal energy stores

A larger braking force means a larger which can be dangerous as brakes could overheat or car could skid

42

## What is another equation for momentum? (Kg m/s)

### Momentum (kg m/s) = mass (kg) x velocity (m/s)

43

## What does the conservation of momentum state?

###
In a closed system, the momentum before an event is the same after the event.

Eg if momentum before was 0, it would be 0 after

44

## What is 'uniform acceleration' ?

### When the acceleration is constant.

45

## What is inertia?

### The resistance an object has to a change in its state of motion

46