Mechanics Flashcards

1
Q

What are Scalar Quantities?

A

Scalar quantities have MAGNITUDE ONLY

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2
Q

What are Vector Quantities?

A

Vector quantities have MAGNITUDE and DIRECTION

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3
Q

What is magnitude?

A

Magnitude represents the size or extent of something, so scalar and vector quantities both indicate the size of them

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4
Q

How can Vector quantities be represented?

A

Through an ARROW, where the size of the arrow represents magnitude, and the direction in which it points represents the direction

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5
Q

Scalar Quantities examples…

A
  • Mass
  • Current
  • Time
  • Distance
  • Energy
  • Speed
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6
Q

Vector Quantities examples…

A
  • Force
  • Velocity
  • Weight
  • Displacement
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7
Q

How does one combine PARALLEL Vectors?

A

They simply ADD UP

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8
Q

How does one combine non-parallel Vectors?

A

One can use the TIP TO TAIL rule or the PARALLELOGRAM rule

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9
Q

What does the Gradient represent in a Distance Time graph?

A

Speed

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10
Q

What does the gradient represent in a speed time graph?

A

Acceleration

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11
Q

How does one find the distance travelled in a speed time graph?

A

Calculate the area under the graph…

How to work it out…

S = D/T

D = ST

D = 10 x 5 (eg)

D = 50m

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12
Q

How does one calculate the speed at a single point in the graph?

A

One must use a TANGENT, which is a line Parallel to the point in the graph

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13
Q

what is a contact force

A

A contact force is a force acting between two objects where the objects are PHYSICALLY TOUCHING

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14
Q

What are some examples of contact forces?

A

Friction, Air resistance, Tension, Normal contact force

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15
Q

what is a non-contact force

A

Non-contact forces are forces that act between two objects that are PHYSICALLY SEPARATED.

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16
Q

What are some examples of non-contact forces?

A

Gravity, Electrostatic force, Magnetic

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17
Q

What is Newton’s First Law?

A

Newton’s first law states that ‘A body will not change its motion unless acted on by an external force’

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18
Q

What is Inertia?

A

Inertia is related to Newton’s 1st Law. Object with a GREATER MASS have MORE INERTIA, so it takes MORE FORCE to change their motion.

Inertia is the tendency of an object to RESIST a change in MOTION

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19
Q

What is Inertial Mass?

A

Inertial Mass is the MEASURE of an object’s RESISTANCE to ACCELERATION

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20
Q

What is the equation for Weight?

A

W = M x G

N) = (kg) x (N/KG

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21
Q

What is the equation for Density?

A
D             =      M        ÷          V
(kg/cm^3)      =     (kg)      ÷      (cm^3)
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22
Q

What is Newton’s second law of Motion?

A

If a force accelerates an object, the rate of acceleration is directly proportional to the mass of the object

F = MA

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23
Q

What is the equation for Force?

A

F = M x A

(N) = (kg) x (m/s^2)

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24
Q

What is the equation for Acceleration?

A

Acceleration = (Final Speed - Start Speed)/ Time

 A = ΔV/ΔT
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25
Q

What does constant force aim to prove in F = MA?

A

If the force is constant, acceleration is inversely proportional mass

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26
Q

What does constant mass aim to prove in F = MA?

A

If the mass is constant, acceleration is directly proportional to force

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27
Q

What does directly proportional mean?

A

If you double one, the other one doubles too

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28
Q

What does inversely proportional mean?

A

If you double one, you half the other one too

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29
Q

If a force of 10N is applied to a ball of mass 1kg, how fast will it move? Will it be faster that a ball of 0.05kg?

A

The 1kg ball will move 10 m/s^2, while the 0.05kg one will move 20 times faster, at 200m/s^2

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30
Q

What is Newton’s 3rd Law?

A

Whenever two objects INTERACT, they exert EQUAL and OPPOSITE FORCES on EACHOTHER

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31
Q

When labelling force on an object, where does the arrow start?

A

At the centre of mass.

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32
Q

Remember…

A

The forces may be EQUAL and OPPOSITE, however the EFFECTS may not be

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33
Q

What is the key condition when considering Newton’s Third law?

A

The forces must be of the SAME TYPE, eg. Gravity against Gravity, REACTION AGAINST REACTION

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34
Q

What is the Braking Distance?

A

The distance a vehicle travels under the BRAKING FORCE

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35
Q

What is the Thinking Distance?

A

The distance a vehicle travels during the THINKING FORCE

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36
Q

What is the Stopping Distance?

A

The stopping distance is the sum of the braking distance and the stopping distance

37
Q

Remember…

A

Work Done = ENERGY

38
Q

Note…

A

THE THINKING DISTANCE IS LINEAR ON A GREAPH IN A TEST

39
Q

Note…

A

THE BRAKING DISTANCE IS A CURVE ON THE GRAPH IN A TEST

40
Q

What is SUVAT?

A

SUVAT is the UNIFORM ACCELERATION EQUATIONS

41
Q

What does SUVAT stand for?

A
S = Displacement
U = Initial velocity
V = Final velocity
A = Acceleration
T = Time (Overall)
42
Q

What are the SUVAT equations to calculate acceleration ON SPECIFICATION?

A

A = (V - U)/T

V^2 - U^2 = 2as

43
Q

What is the formula for Momentum?

A

P = M x V

kg m/s) = (kg) x (m/s

44
Q

What is the rule of conservation of momentum?

A

In a closed systen, the total momentum before an event is equal to the total momentum after the event

45
Q

Note on Force in relation to Momentum…

A

FORCE IS EQUAL TO THE CHANGE IN MOMENTUM!

A = (V - U)/T

F = MA

F = M((v - u)/t)

F (mv - mu)/t

i.e. Force = Change in Momentum

SO FORCE IS EQUAL TO CHANGE IN MOMENTUM

46
Q

What is the Equation for Change in Momentum

A

FT = ΔP

47
Q

Is momentum a vector or a scalar?

A

Momentum is a VECTOR quantity

48
Q

Have a break :)

A

Go ahead XD

49
Q

What is a Moment?

A

A MOMENT is a TURNING EFFECT of a FORCE

50
Q

What is the Equation for a Moment?

A

Moment = FD

51
Q

What is important to remember when calculating the moment?

A

Moment = Force x Perpendicular distance from the pivot to the line of action of the force

52
Q

What is the correct terminology for left and right when describing direction of moments?

A

Clockwise and Anticlockwise

53
Q

What happens when CLOCKWISE moments and ANITCLOCKWISE moments are EQUAL?

A

They are in equilibrium

54
Q

What is the centre of Mass / Gravity?

A

The centre of mass is where a body behaves as of its whole mass were concentrated at one point… This means the body’s weight can be considered to act at this point

55
Q

What can one do to increase stability?

A

One can lower the centre of mass, or increase the area of the base

56
Q

WHAT IS THE UNIT WHICH ALL QUESTIONS SHOULD BE ANSWERED TO DO WITH MOMENTS IN AN EXAM?!

A

NEWTON METRES (NM)

57
Q

What are Levers?

A

Levers allow a larger force to act upon the load than is supplied by the effort. This makes it easier to move larger or heavier objects

58
Q

How does the size of the lever affect the force?

A

The larger the lever, and the further the effort acts on a point, the greater the force on the load will be

59
Q

How do Levers involve moments?

A

Levers make use of moments to act as a FORCE MULTIPLIER

60
Q

What do gears rotate on?

A

Their AXLE or SHAFT

61
Q

What directions do gears rotate in?

A

Gears rotate in OPPOSITE DIRECTIONS

62
Q

Note on Larger Gears…

A

If a larger gear is driven by a smaller gear, the larger gear will rotate slowly, but will have a GREATER MOMENT. For example, a low gear in a bike or a car

63
Q

Note on Smaller Gears…

A

If a smaller gear is driven by a larger gear, the gear will rotate quickly, but will have a SMALLER MOMENT. For example, a high gear on a bike or a car

64
Q

What do gears do? (force)

A

They act as a TURNING EFFECT MULITPLIER

65
Q

What is the significance of the amount of teeth in gears?

A

Gears with different numbers of teeth change the rate of rotation

66
Q

What is Hooke’s Law?

A

The extension of a spring is directly proportional to the force applied, provided that the limit of proportionality is not exceeded

67
Q

What is the equation for the potential energy of a spring?

A

1/2 x Spring Constant x Extension of spring

68
Q

Weight

A

The force acting on a mass due to gravitational attraction

69
Q

Electrostatic force

A

The force between two charged objects

70
Q

Thrust

A

The force causing an object to move

71
Q

Air resistance

A

Friction in the air on a moving object

72
Q

Upthrust

A

Force of a fluid pushing an object upwards

73
Q

Compression

A

Forces that act inwards on an object, squeezing it

74
Q

Tension

A

Force transmitted through a cable when pulled on by forces acting on its opposite ends

75
Q

Reaction force

A

A force due to contact between two objects

76
Q

What is the centre of mass?

A

The point at which all the weight of an object acts

77
Q

What is the equation for weight?

A

W = MG

Weight = Mass X Gravity

78
Q

What is the resultant force?

A

The single force that describes all the forces operating on a body

79
Q

Where does tension act?

A

Away from the mass

80
Q

What is work done?

A
  • Object moves over certain distance
  • By a force
  • In specific direction
81
Q

What must happen for a stationary object to change its shape?

A
  • Stretching (forces in opposite directions AWAY from object)
  • Bending (forces that distort the object)
  • Compression (forces acting in opposite directions TOWARDS object)
82
Q

What are the two types of deformation?

A

Elastic, Inelastic

83
Q

What is elastic deformation?

A

When an object returns to their original shape when the stretching force is removed.

eg. Rubber bands, steel springs

84
Q

What is inelastic deformation?

A

When an object remains stretched and does not return completely to its original shape when stretching force is removed

eg. Plastic, clay, glass

85
Q

What is the equation for Hooke’s law?

A

F = ke

F = Force
K = Spring constant
E = Extension in metres
86
Q

What is the spring constant?

A

How stiff a spring is. The higher the spring constant is, the higher the stiffness

87
Q

Systematic Errors

A

Parralax errors taken from, eg. Misreading data

88
Q

Random Errors

A

Poor accuracy from, eg. Low resolution