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Physics A-level Year 1 > 2.1 - Motion > Flashcards

2.1 - Motion Flashcards

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1
Q

How do we calculate rate of movement (speed)

A

Speed = distance / time

V = d/t

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2
Q

What is velocity

A

When you include the direction in the information about the rate of movement of an object - this is velocity

It’s the rate of change of displacement - wher the distance in a particular direction is called the displacement

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3
Q

What’s displacement

A

The distance in a particular direction

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4
Q

How is velocity calculated

A

Velocity = displacement / time

V = s/t

Or v = little triangle s / little triangle t

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5
Q

What’s a vector

A

A quantity in which the direction must be stated is known

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6
Q

What’s a scalar quantity

A

If direction is not important - the measurement is referred to as a scalar quantity

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7
Q

How are vectors notated ? (Idk if it’s just the way the book does it or if it’s true irl lol)

A

Vector notation means that vectors are written in bold type to distinguish them from scalar variables

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8
Q

How is average speed calculated

A

Calculated by dividing the total distance for a journey by the total time for the journey - thus it averages Out the slower and faster parts off the journey and even includes stops

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9
Q

What’s acceleration

A

It’s defined as the rate of change of velocity, therefore it must include the direction in which the speed is changing and so acceleration is a vector quantity

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10
Q

How can we calculate acceleration

A

Change in velocity / time taken to change the velocity

a = (v - u)/ t

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11
Q

What is the vector nature of acceleration

A

If an object changes just the direction of its velocity, it’s accelerating whilst remaining at a constant speed

Similarly, deceleration represents a negative change in velocity and so could be quoted as a negative acceleration

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12
Q

What’s the greatest speed possible

A

No speed or velocity can ever be greater than the speed of light which is 3 x 10^8 m/s

If one calculates a speed higher than this, one must be wrong m8 ya idiet

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13
Q

Define speed

A

The rate of change in distance

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14
Q

Define velocity

A

The rate of change of displacement

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15
Q

Define displacement

A

The vector measurement of distance in a certain direction

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16
Q

Define a vector

A

A vector quantity must have both magnitude and direction

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17
Q

Define a scalar

A

A scalar quantity only has magnitude

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18
Q

Define average speed

A

Calculated by dividing the total distance for a journey by the total time for the journey

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19
Q

Define instantaneous speed

A

Is the speed at any particular instant in time on a journey, can be found from the gradient of the tangent to a distance time graph at that time

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20
Q

Define acceleration

A

Is the vector defined as the rate of change of velocity

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21
Q

How can a velocity time graph be generated

A

Can be produced from direct measurements of the velocity or generated from calculations made using a displacement time graph

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22
Q

What da difference with displacement and distance graphs against time

A

Displacement time graphs can have a decreasing displacement y value whereas a distance time graph y value can only increase !

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23
Q

What can we find out from displacement time graphs / distance graph

A

Simplest thing is how far an object has moved in a certain amount of time

A flat line bit means the object is stationary

The gradient tells us the speed - found from the ratio of change of y axis divided by x axis
- distance / time
Or displacement / time

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24
Q

What does a velocity time graph show

A

Shows the velocity of an object over time

For velocity we can also tell the direction with the y value being positive or negative

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25
Q

How can we calculate acceleration from a velocity time graph

A

We must divide a change in velocity by the corresponding time difference to find the gradient and so acceleration.

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26
Q

How can we calculate th distance travelled from a v-t graphs

A

We must calculate the areas from between the lines of the graph and axis

Add the areas to get total distance

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27
Q

How can we find the acceleration due to gravity by multiflash photography

A

Using multiflash photography technique, or a video recording that can be played back frame by frame - we can observe the falling motion of a small object such as a marble, we need to know the time between frames

From each image of the falling object, measure the distance it has fallen from the scale in the picture, a carefully drawn distance time graph will show a curve as the object accelerates, from the curve, take regular measurements of the gradient using tangents of the curve - making instantaneous speeds, plotting these speeds on a velocity time graph should show a straight line - as acceleration from gravity is constant. The gradient of line will be acceleration due to gravity

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28
Q

What do acceleration time graphs show

A

Shows how the acceleration of an object changes over time,

Curve will change as acceleration changes due to changes in air resistance etc

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29
Q

What happens if the distance time graph line is curved

A

It’s a changing velocity - so acceleration or deceleration is happening

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30
Q

Define a displacement time graph

A

A graph showing the positions visited on a journey - with displacement on the y axis and time on the x axis

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31
Q

Define a velocity time graph

A

A graph showing the velocities in a journey, with velocity on the y axis and time on x axis

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32
Q

What’s deceleration on a distance time graph line look like

A

Going into a n shape kind of

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33
Q

What does acceleration look like on a distance time graph look lik

A

Like a u - like the 2nd half of the u

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34
Q

What time of quantity are forces

A

Vectors

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35
Q

What does using vector addition tell us

A

We can add and subtract all forces to work out the resultant force

Add forces in the same direction and subtract if they are in opposite direction

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36
Q

How can we describe the resultant force

A

We can consider it as the single force that has the same effect as all the Individual forces combined

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37
Q

How can we calculate a resultant forces if they’re perpendicular

A

Use soh cah toa

Or Pythagoras if ya want babez 🙈

Trigonometry will determine angle / direction is the resultant

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38
Q

How should we state the angle of a resultant force from perpendicular forces

A

The angle should be stated as from the horizontal, and draw the angle on the triangle thing to clearly show the angle

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39
Q

How can we find out the resultant of 2 non perpendicular forces

A

We draw the forces on make a triangle some way and use trig

Check pg 21 or text book lolz

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40
Q

What’s the parallelogram rule FOR

A

finding the resultant of 2 non perpendicular forces or vectors by a scale drawing, draw vectors to scale, draw the same vectors to make a parrelogrsm (lol just check pg 22 to see) ,

Then draw a line joining 2 sides to make the longest possible line which will be the hypotenuse
- will be the diagonal across the parallelogram from the starting point

41
Q

Omg wait what if there more than 2 vectors ?

A

Add 2 together and then add to another and another until, all have been added in yes

42
Q

What are free body diagrams for

A

If we clarify what forces are acting on an object, it can be simpler to calculate how it will move - to do this be usually draw a free body diagram

The object is isolated and all the forces that act on it are drawn in at the points they act from ,

Other objects not drawn, only the effect these objects have on the original object you drawing free body diagram of - only the force from that object drawn on

Ya get me

43
Q

Define the resultant force

A

It’s the total force (vector sum) acting on a body when all the forces acting are added together accounting for their directions

44
Q

Define a free body diagram

A

A free body diagram of an object has the object isolated and all the forces that act on it are drawn in at points where they act, using arrows to represent the forces

45
Q

How can forces affect an object

A

It may bend or rotate

46
Q

When might an object bend when a force is applied

A

If the object is fjxed so it can’t rotate - it will bend

47
Q

When might an object rotate

A

When a force is applied, an object does not start to move Along but instead rotate about a fixed pivot point

48
Q

What is the moment of a force

A

The tendency to cause rotation is called the moment of a force

49
Q

How do we calculate the moment of a force

A

Moment (Nm) = force (N) x perpendicular distance from the pivot to the line of action of the force (m)

M=fx

50
Q

What direction will an object move when a force is applied

A

A body will turn in the direction of any net moment

51
Q

What’s the principle of moments

A

The sum of the clockwise moments is equal to the sum of anti-clockwise moments when a body is in rotational equilibrium

52
Q

What’s rotational equilibrium

A

This means the object will remain stationery or if it’s already rotating it will continue at the same speed in the same direction

The sum of all forces acting on the object is 0

53
Q

What if there’s more than one moment in the same direction

A

Calculate individual moments and then add them together

54
Q

What’s the centre of gravity

A

The weight of an object is caused by the gravitational attraction between the earth and each particle contained within the object. The sum of all these tiny weight forces appears to act from a single point in any object - the centre of gravity

55
Q

How do the calculate the centre of gravity for a symmetrical object

A

We can calculate the centre of gravity as it must lie on every line of symmetry - the point of intersection is the centre of gravity

56
Q

What’s the centre of gravity also equal to

A

The centre of mass - the point is identical for objects that are small compared to the size of the earth

57
Q

How do we work out the centre of gravity for irregular shaped objects

A

It’s the point at which it’s weight appears to act on the object

Eg a Bunsen burner has a heavy base so the centre of gravity is low down near the concentration of mass as there will be greater attraction by the earths gravity to this large mass

58
Q

How can we investigate finding the centre of mass of an irregular rod

A

We use the principle of moments, try balance the rod , if it’s a broom - it will be difficult to do thus exactly so we can use an alternative method, measure the mass of the rod then use a set of hanging masses on the rod to balance it more in the middle and then calculate the clockwise moment to the anti clockwise moment and then calculate the distamce and that’s the centre of gravity ? Pg 25

59
Q

Define a body in equilibrium

A

It’s in equilibrium if there is a zero resultant force and zero resultant moment, it will have a zero acceleration

60
Q

Define the principle of moments

A

States a body will be in equilibrium if the sum of clockwise moments acting on it is equal to the sum of the anti clockwise moments

61
Q

Define the centre of gravity of an object

A

It’s the point through which the weight of the object appears to act

62
Q

What is Newton’s first law of motion

A

If an object is stationary, there needs to be a resultant force to make it more. If the object is already moving, it will continue at the same speed in the same direction unless a resultant force acts on it.

If there is no resultant force on an object, either because no forces are acting on it or all the forces balance out - then the objects motion is unaffected

63
Q

What is Newton’s second law of motion

A

This law tells us how much of an objects motion will be changed by a resultant force, for an object with constant mass, it’s usually written as

F = ma
(Resultant force = mass x acceleration)

64
Q

How can we investigate Newton’s second law in an experiment

A

Set up an experiment with a data logger, laptop, light gates and a trolley in motion , change the masses that make trolley accelerate

Measure the acceleration- draw a graph if it’s a straight line this means this means acceleration is proportional to resultant force

You can do a graph of acceleration against 1/mass to show acceleration is inversely proportional to mass
Investigation demonstrates a = f/ m
- rearrangement of Newton’s second law

65
Q

When can a graph be described as directly proportional

A

Y = mx + c

If c =0 , the line will pass through the origin it’s directly proportional

66
Q

What are most types of physics relationships

A

Causal relationships - eg acceleration is caused by force

Rarely are they statistical correlation so describing a graph as having a positive correction may not be appropriate babes

Ooooo inaProPriaTE bEHavioUr

67
Q

What is Newton’s third law of motion

A

When object a causes a force on another object b, then object b causes an equal force in the opposite direction to act upon object a,

Every force has an equal and opposite reaction force

68
Q

Define simply Newton’s first law of motion

A

An object will remain at rest, or in a state of uniform motion, until acted upon by a resultant force

69
Q

Define Newton’s second law of motion simply

A

If an objects mass is constant, the resultant force need to cause an acceleration is given by f = ma

70
Q

Define Newton’s third law of motion simply

A

For every reaction, there is an equal and opposite reaction

71
Q

What is kinematics

A

The study of the movement of objects, use equations known as SUVAT equations to find out details about the motion of objects accelerating in one direction

72
Q

What is uniform motion

A

If an object has no resultant force acting on it then it does no accelerate - this is uniform motion

In this situation we involve only simply v = s/t equation

As velocity at the start is the same as the end

73
Q

What are the variables of suvat equatjons

A

We can work out the variables for an object with constant acceleration

S - displacement
U - initial velocity
V - final velocity
A - acceleration 
T - time
74
Q

Tell me about finding a variable with suvat equations

A

Each equation has 4 variables, which means if we know the values of any 3 variables, we can find out the other 2

75
Q

If an object is falling what variable do we already know

A

A = 9.81 due to gravity

a= g

76
Q

Can we combine equations

A

Yes, substitute different variable equations in to work out stuff

77
Q

Hol up what if there’s 2 equations I Could use

A

Use either lol we should get the same answer lol

78
Q

Tell me suvat equation where distance is not used

A

V = u + at

79
Q

Tell me suvat equation where acceleration not used

A

S = (u + v)/2 x t

80
Q

Tell me about suvat equation not including final velocity

A

S = ut + 1/2at^2

81
Q

Tell me about the suvat equation not including time

A

V^2 = u^2 + 2as

82
Q

Can I use suvat equatjons if acceleration is changing?

A

NO NO NO NOOOO

83
Q

How can we investigate finding the acceleration due to gravity by free fall

A

A system for timing the fall of an object under gravity can allow us to measure the acceleration due to gravity

Measure time to fall from a certain height, then alter the height and measure again

We can use suvat to work out the time and height and plot time against height, we can use a line of best fit to calculate gravity (a)

84
Q

How can we reduce uncertainty from single measurements

A

A single measurement in any experiment is prone to uncertainty from random and systematic error, we can reduce these by

Taking many readings and plotting a graph which leads to much more reliable conclusions

85
Q

Define kinematics

A

It’s the study of the description of the motion of objects

86
Q

Define uniform motion

A

It’s the Motion when there is no acceleration

Velocity = displacement/time

87
Q

What is resolving vectors or resolution

A

FIND the 2 vectors that make the overall vector that starts from the same point as the other 2

88
Q

How can we resolve vectors

A

We need an angle, between either the vertical or horizontal component and then use trigonometry to split it up

We can also use a scale diagram

The pair of vectors must be right angles to each other

You can continue to resolve new vectors after working out 2, then work out vectors parallel and perpendicular and stuff Or something idk

89
Q

Define resolution or resolving vectors

A

The determination of a pair of vectors at right angles to each other that sums to give the single vector they were resolved from

90
Q

What motion to objects thrown or fired tend to have

A

A projectile motion

91
Q

How do vectors acting at right angles act

A

They act INDEPENDENTLY consider them on their own, their combined effect can be calculated with vector addition but they can also be considered to act separately and at the same time - this would cause independant effects which themselves could be combined to see an overall effect

92
Q

‘Physics is holistic’ - what this mean

A

You can apply any rule to all things. Physics is a set of rules to explain everything in the universe

93
Q

What do we consider about the motion when an object has been thrown or whatever

A

We only consider the motion after the force projecting an object has finished

Eg if something fired from a cannon, after cannon fired ,air resistance is ignored - the only force acting considered is the objects weight

94
Q

What happens when a object is thrown horizontally

A

When an object is projected horizontally, it will start off with zero vertical velocity, however gravity will act on it so that it’s motion will curve downwards, in a parabola shape

95
Q

What’s different about a vertical component to horizontal

A

Horizontal had no accelerating force for. Gravity or anything so just use v = d/t to calculate things

Use suvat for vertical,

96
Q

How can we recombine velocity components

A

Adding the vertical and horizontal components into their resultant using trig

97
Q

Tell me about the trajectory of a vertical throw

A

If a ball goes up forward, at the highest point the vertical velocity is momentarily 0

A vertical upwards component of motion will have a symmetrical trajectory

Getting to the highest point will take half the time of the whole flight

98
Q

Define a projectile

A

It’s a moving object on which the only force of significance acting is gravity. The trajectory is pre determined by its initial velocity

Physics A-level Year 1 (13 decks)

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