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Physics > Motion > Flashcards

Motion Flashcards

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1
Q

Distance

A

How far an object moves
But not what direction it moves in

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2
Q

What quantity is distance?

A

Scalar
It has a measurement of how far it moved but not what direction

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3
Q

Displacement

A

The distance an object moves from start to finish
Only shown as a straight line, not the turns it could take
Include direction if that line eg north east or west

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4
Q

What quantity is displacement?

A

Vector
Because it is a measure of how far it travelled and the direction

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5
Q

Speed

A

Tells us the distance something travelled in a given time

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6
Q

What quantity is speed?

A

Scalar because it doesn’t have a direction

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7
Q

How to find speed (m/s)

A

Distance (m)
—————
Time (s)

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8
Q

What’s different about the speed/distance/time equation?

A

Distance represented by symbol S
Speed represented by symbol V

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9
Q

Normal walking speed

A

1.5m/s

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10
Q

Running speed

A

3m/s

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11
Q

Cycling speed

A

6m/s

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12
Q

What do non mechanical speeds (walking, running etc) depend on?

A

Who the person is, a fitter/younger person may move quicker than older/unfit
Terrain, people move quicker on flat ground
Than uphill
Distance travelled, people move quicker at the beginning of a long distance route when more energy

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13
Q

Car on main road speed

A

13m/s

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14
Q

Fast train in Uk speed

A

50m/s

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15
Q

Cruising aeroplane speed

A

250m/s

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16
Q

Speed or sound in air

A

330m/s

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17
Q

Is speed of a losing object always constant?

A

No
It changes on its journey ie a car slowing down and speeding up

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18
Q

Even though speed is usually not constant, how do we find a value for calculations?

A

We use the average speed over the cause of the journey

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19
Q

Equation for distance

A

Speed (m/s) x time (s)

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20
Q

Velocity

A

An objects speed in a certain direction
For example it says north, east, south, west

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21
Q

Speed vs velocity

A

For example:
Speed = 20m/s
Velocity = 20 m/s east

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22
Q

What quantity is velocity?

A

Vector
Because it gives us a measure of speed and the direction it is in

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23
Q

How do we calculate velocity?

A

The same way we find speed
(Distance/time)
But you MUST write the direction NEXT to it

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24
Q

When is the velocity value different?

A

When objects move in a circle

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25
Q

How does velocity change in objects moving in a circle?

A

If it moves at a constant speed in a circle/ part of a circle
The velocity constantly changes
Because it’s direction changes although the speed is the same
This is because to calculate the velocity, distance is a value you need to know as well

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26
Q

Distance time graphs

A

How we can show a distance an object travelled in a journey
Over the course of a given time
Also can calculate speed using it

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27
Q

When can we draw a distance time graph?

A

If the object moves in a straight line

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28
Q

How do distance time graphs look?

A

DISTANCE (m) on y axis
TIME (s) on x axis

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29
Q

What happens when someone stops walking in a distance time graph?

A

The line is straight
There is a point when they first stop
Connected to another point when they finish stopping
Straight line because the distance doesn’t increase = they have stopped

30
Q

What do you need to be sure of when plotting distance time graph?

A

Make sure you add the time to the time
and the distance to the distance
DO NOT MIX THEM UP AND ADD DISTANCE TO TIME

31
Q

On a distance time graph what does the gradient show?

A

The speed!!!!!

32
Q

If the distance time graph is an upwards slope, what does it tell us?

A

It is constantly increasing/ decreasing speed
Aka it’s accelerating or decelerating

33
Q

How to find the speed at a specific point if the distance time graph is a slope?

A

Put a point in the graph at the specified point
Draw a tangent as large as possible
Use that to make a triangle and do distance / time = speed

34
Q

Acceleration

A

Tells us the change in velocity of an object over a given time

35
Q

Unit for acceleration

A

m/s²

36
Q

How do we find the acceleration?

A

Change in velocity (m/s)
————————————
Time (s)

37
Q

What does acceleration tell us?

A

Every second, the object increased by the acceleration value every second over the given time period

38
Q

What happens if the starting velocity is more than the end velocity when calculating acceleration

A

The velocity decreases
Thus the change is negative
So the acceleration is negative =deceleration

39
Q

How else can we find the acceleration not using equations?

A

Velocity time graphs

40
Q

Velocity time graphs

A

Shows us the objects change in speed in a certain direction over a period of time

41
Q

How do velocity time graphs look like?

A

Y axis = velocity (m/s)
X axis = time (s)

42
Q

What does a changing gradient on a distance-time graph show?

A

THE ACCELERATION!!!
if it’s straight = constant speed. Not acceleration
Positive gradient = acceleration = upward slope
Negative gradient = deceleration = downward slope

43
Q

If the line is flat on a velocity time graph what does that show.

A

That it’s moving at a constant velocity
It isn’t accelerating
NOT THAT IT HAS STOPPED, OTHERWISE IT WOULD GO DOWN TO 0 ON THE Y AXIS!!!!

44
Q

What does the area below the graph on a velocity time graph show?

A

The distance travelled in a specific direction = displacement
In m

45
Q

What equation can we use if an object accelerates at a constant rate?

A

V² - u² = 2Ad

V = final velocity
U = initial velocity
A = acceleration
D = distance

46
Q

If an object falls to the surface of the Earth, what is the initial acceleration and why?

A

9.8m/s²
Because of the force of gravity acting on the object

47
Q

As an object falls to the surface of the Earth, why does the initial acceleration change?

A

As it falls it experiences upward force of friction due to air particles
Aka air resistance
And the force of air resistance balances the force due to gravity
Therefore it stops accelerating and moves at a constant velocity

48
Q

Terminal velocity

A

When the force of gravity balances the force of air resistance as an object falls to surface of the Earth
Thus it moves at a constant velocity and doesn’t accelerate

49
Q

What does terminal velocity apply to?

A

Objects in liquid
Objects falling to surface of the Earth (liquid is air)

50
Q

What determines the terminal velocity of an object?

A

How much friction an object experiences (based on shape)
Greater force of friction = lower terminal velocity

51
Q

Newtons laws of motions

A

Describes the effects that forces have on the motion of an object

52
Q

Newtons FIRST law of motion

A

If the resultant force acting on a STATIONARY object is zero, it will stay STILL
If the resultant force acting on a MOVING object is zero, it continues moving in the SAME DIRECTION at the SAME SPEED (SAME VELOCITY)

53
Q

So how will the velocity of an object change?

A

If a resultant force of above 0N acts on the object

54
Q

If a car is moving at a constant speed what is its resultant force?

A

0N

55
Q

Resistive forces

A

Forces that act against the forward force of an object

56
Q

Examples of resistive forces

A

Friction on the ground
Air resistance in air

57
Q

If an object is moving to the right and a resultant force is applied to the RIGHT, what happens?

A

It will accelerate to the right
Aka it’s velocity will increase

58
Q

In an object is moving to the right and a resultant force is applied to the LEFT, what happens?

A

It will decelerate but continue moving to the right
Because the resultant force still pushes to the right
Aka it’s velocity will decrease

59
Q

If an object is moving up and a resultant force pushes upwards, what happens?

A

It will accelerate upwards
Because resultant forces can also change an objects direction
Because it affects velocity that affects direction

60
Q

Newtons SECOND law

A

The acceleration of an object = proportional to the resultant force
And inversely proportional to mass of object

61
Q

What does Newton’s second law mean in practise?

A

Bigger resultant force = bigger acceleration
Smaller resultant force = smaller acceleration
Which is directly proportional

Bigger mass = smaller acceleration
Smaller mass = bigger acceleration
Inversely proportional

62
Q

How to find force needed to accelerate an object?

A

Force = mass x acceleration

63
Q

Speed of cars on main road in uk

A

13 m/s

64
Q

Speeed of cars on motorway

A

30m/s

65
Q

What do cars need to accelerate from a main road to motorway?

A

2m/s^2

66
Q

What force would need to accelerate a typical family car by 2m/s^2

A

2000N

67
Q

Inertia

A

The property of mass that obeys newtons 1st law
That they will keep still or keep the same motion if you apply resultant force

68
Q

Inertial mass

A

Measure of how difficult it is to change the velocity of an object

69
Q

Large inertial mass

A

Requires large force to produce a given acceleration
Because it has more inertia
So it’s harder to apply enough force to overpower the resistive forces

70
Q

Newtons THIRD law

A

Whenever 2 objects interact the forces they exert on each other are equal and opposite
(Write this word for word in exam)

71
Q

What does Newton’s third law mean in practise?

A

If you exert a force on an object, it will exert a force on you back which is equal in size
But opposite in direction

72
Q

Inertial mass equation

A

Resultant force
————————
Acceleration

Physics (44 decks)

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