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Motion Flashcards

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
How does velocity change in objects moving in a circle?
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
26
Distance time graphs
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
27
When can we draw a distance time graph?
If the object moves in a straight line
28
How do distance time graphs look?
DISTANCE (m) on y axis TIME (s) on x axis
29
What happens when someone stops walking in a distance time graph?
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
What do you need to be sure of when plotting distance time graph?
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
On a distance time graph what does the gradient show?
The speed!!!!!
32
If the distance time graph is an upwards slope, what does it tell us?
It is constantly increasing/ decreasing speed Aka it’s accelerating or decelerating
33
How to find the speed at a specific point if the distance time graph is a slope?
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
Acceleration
Tells us the change in velocity of an object over a given time
35
Unit for acceleration
m/s²
36
How do we find the acceleration?
Change in velocity (m/s) ———————————— Time (s)
37
What does acceleration tell us?
Every second, the object increased by the acceleration value every second over the given time period
38
What happens if the starting velocity is more than the end velocity when calculating acceleration
The velocity decreases Thus the change is negative So the acceleration is negative =deceleration
39
How else can we find the acceleration not using equations?
Velocity time graphs
40
Velocity time graphs
Shows us the objects change in speed in a certain direction over a period of time
41
How do velocity time graphs look like?
Y axis = velocity (m/s) X axis = time (s)
42
What does a changing gradient on a distance-time graph show?
THE ACCELERATION!!! if it’s straight = constant speed. Not acceleration Positive gradient = acceleration = upward slope Negative gradient = deceleration = downward slope
43
If the line is flat on a velocity time graph what does that show.
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
What does the area below the graph on a velocity time graph show?
The distance travelled in a specific direction = displacement In m
45
What equation can we use if an object accelerates at a constant rate?
V² - u² = 2Ad V = final velocity U = initial velocity A = acceleration D = distance
46
If an object falls to the surface of the Earth, what is the initial acceleration and why?
9.8m/s² Because of the force of gravity acting on the object
47
As an object falls to the surface of the Earth, why does the initial acceleration change?
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
Terminal velocity
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
What does terminal velocity apply to?
Objects in liquid Objects falling to surface of the Earth (liquid is air)
50
What determines the terminal velocity of an object?
How much friction an object experiences (based on shape) Greater force of friction = lower terminal velocity
51
Newtons laws of motions
Describes the effects that forces have on the motion of an object
52
Newtons FIRST law of motion
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
So how will the velocity of an object change?
If a resultant force of above 0N acts on the object
54
If a car is moving at a constant speed what is its resultant force?
0N
55
Resistive forces
Forces that act against the forward force of an object
56
Examples of resistive forces
Friction on the ground Air resistance in air
57
If an object is moving to the right and a resultant force is applied to the RIGHT, what happens?
It will accelerate to the right Aka it’s velocity will increase
58
In an object is moving to the right and a resultant force is applied to the LEFT, what happens?
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
If an object is moving up and a resultant force pushes upwards, what happens?
It will accelerate upwards Because resultant forces can also change an objects direction Because it affects velocity that affects direction
60
Newtons SECOND law
The acceleration of an object = proportional to the resultant force And inversely proportional to mass of object
61
What does Newton’s second law mean in practise?
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
How to find force needed to accelerate an object?
Force = mass x acceleration
63
Speed of cars on main road in uk
13 m/s
64
Speeed of cars on motorway
30m/s
65
What do cars need to accelerate from a main road to motorway?
2m/s^2
66
What force would need to accelerate a typical family car by 2m/s^2
2000N
67
Inertia
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
Inertial mass
Measure of how difficult it is to change the velocity of an object
69
Large inertial mass
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
Newtons THIRD law
Whenever 2 objects interact the forces they exert on each other are equal and opposite (Write this word for word in exam)
71
What does Newton’s third law mean in practise?
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
Inertial mass equation
Resultant force ———————— Acceleration

Physics (44 decks)

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