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let's get physical! > 2. the bull I ride is not mechanical [COMPLETE] > Flashcards

2. the bull I ride is not mechanical [COMPLETE] Flashcards

mechanics

1
Q

What is mass?

A

the amount of matter something contains, kg

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2
Q

What is weight?

A

the force due to gravity pulling two objects together, N

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3
Q

What is g?

A

The acceleration due to gravity

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4
Q

What is normal contact force?

A

a force perpendicular to a surface stopping two objects crushing together.

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5
Q

What is tension?

A

a force which can be due to compression of stretching of a material

it always comes in pairs

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6
Q

What is tension due to stretching?

A

the materials molecules are pulled apart and an attractive electromagnetic force between the molecules pulls them back together

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7
Q

What is tension due to compression?

A

the material molecules are pushed together and a net repulsive electromagnetic force tries to push them further apart

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8
Q

What is friction?

A

a force that acts against motion between two surfaces in contact.

parallel to motion in the opposite direction

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9
Q

What does the size of a frictional force depend on

A
  • type of surface

- how hard the surfaces are pressed together

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10
Q

What is moment?

A

turning effect on an object. It is the product of the distance perpendicular to the force and the force applied.

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11
Q

What is the moment of a force about a point (Nm)?

A

force (N) * perpendicular distance from the force (m)

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12
Q

What is “couple”?

A

two forces that are equal and opposite do not act along the same line meaning there is no resultant force but still a turning effect.

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13
Q

What is the principal of moments?

A

when an object is in equilibrium the sum of clockwise moments about any point equals the sum of anticlockwise moments about the same point

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14
Q

What is the centre of gravity?

A

the point at which we can take its entire weight to act, THERE IS NO MOMENT DUE TO WEIGHT

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15
Q

What is the centre of mass?

A

the point at which we can take the entire mass to be concentrated

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16
Q

What is a stable object?

A

the centre of mass and line of action lies between the objects base/supports

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17
Q

How do you locate the centre of mass?

A

hang the shape from a pivot point with a plum line and nail
trace along the plum line
repeat from at least 2 more pivots
where all the lines cross is the CoM
(the CoM must be along the line of action because there are no resultant moments)

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18
Q

What is distance?

A

how much ground an object has covered during its motion (scalar quantity)

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19
Q

What is displacement?

A

how far out of place an object is and the overall change in the objects position (vector quantity)

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20
Q

What is speed?

A

rate of change of distance

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21
Q

What is velocity?

A

rate of change of displacement

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22
Q

What is acceleration?

A

rate of change of velocity

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23
Q

What do straight lines on a displacement time graph represent?

A

constant velocity (if flat the velocity = 0)

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24
Q

How do you find the instantaneous velocity from a displacement time graph?

A

draw a tangent and find the gradient

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25
Q

How do you find the distance of the journey from a displacement time graph?

A

sum of slope height (not inc negatives)

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26
Q

How do you find the displacement of the journey from a displacement time graph?

A

sum of slope heights inc negatives

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27
Q

How do you find the acceleration from a displacement time graph?

A

find the initial and final velocity at two points by finding the gradient
divide by the time between the two points to get acceleration

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28
Q

What does the gradient of a velocity time graph represent?

A

acceleration

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29
Q

What does the area under a velocity time graph represent?

A

distance/displacement depending on negatives

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30
Q

When can suvat equations be used?

A

when an object moves with constant uniform acceleration

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31
Q

What is free fall?

A

the only force acting on an object is gravity. Accelerate downwards at the same rate

32
Q

What is terminal velocity?

A

the highest attainable velocity of an object as it falls through a fluid. the drag = weight.

terminal velocity can be different speeds i.e. a skydiver will have two different terminal velocities depending on if the parachute is open.

33
Q

When is an object following projectile motion?

A

an object follows a parabolic path

34
Q

How do you approach a projectile question?

A

resolve the initial velocity into horizontal and vertical components
acceleration only acts on the vertical component and is g.
horizontal distance can be easily calculated using the equation s = vt

35
Q

What is Netwon’s first law?

A

an object will remain at rest or travelling at a constant velocity, until it experiences a resultant force

36
Q

What is Newton’s second law?

A

the rate of change of momentum of an object is directly proportional to the resultant force acting on it and will act in the same direction as that force
F = (mv-mu)/t or F=ma

37
Q

What is Newton’s third law?

A

If object A exerts a force on object B then object B exerts an equal and opposite force back on A

38
Q

What are the conditions to have a Newton’s third law pair? (5)

A
  • forces must have the same magnitude
  • forces act along the same line but in opposite directions
  • forces act for/at the same time
  • forces act on a different object
  • forces are the same type
39
Q

What is work done?

A

the energy transferred whenever a force moves an object over a distance. scalar quantity measured in joules.

40
Q

What is the equation for work done?

A

force, F (N) * displacement in the direction of the force, s (m)

41
Q

If the force and displacement are not in the same direction when calculating work done:

A

resolve the force

W = Fcosx * s

42
Q

What is energy?

A

the ability to do work

43
Q

What does 1 joule represent?

A

the work done when a force of 1N moves through a distance of 1m in the direction of the force

44
Q

What is power?

A

rate of doing work

45
Q

What is the equation for power?

A

= work done, w(J) / time takens, t (s)

= force, F (N) * velocity, v (m/s)

46
Q

What is kinetic energy?

A

the energy an object has because of its motion

47
Q

What is the equation for kinetic energy?

A

1/ 2 * m* v^2

48
Q

What is potential energy?

A

the energy stored in an object due to its position, state or shape
e.g. gravitational, chemical, elastic, electrical or nuclear

49
Q

What is the equation for gravitational energy?

A

mgh

50
Q

What is the equation for elastic potential energy?

A

= 1/2Fx

= 1/2 kx^2

51
Q

When is constant velocity achieved?

A

When there is no resultant force and no work is done

52
Q

What is the principle of conservation of energy?

A

energy can be transferred from one form to another, bu it cannot be created or destroyed. The total amount of energy always remains the same.

53
Q

What is efficiency?

A

the proportion of energy that is usefully transferred is called the efficiency of the machine

54
Q

What is the equation for efficiency?

A

useful out/total in

55
Q

List the suvat equations (4)

A

v=u +at
s=(u+v)/2 t
s=ut + 1/2a*t^2
v^2=u^2 + 2as

56
Q

What is a free-body diagram?

A

a free body diagram whoch shows all the forces that act on an object

57
Q

How do you prove N1L using N2L?

A

if resultant force is 0 and acceleration is 0
F=0
a=0
0=m*0
0=0

58
Q

When does terminal velocity occur?

A

when the frictional forces acting on an object and the driving forces are equal, so no resultant, no acceleration, so it travels at constant velocity

59
Q

What is the equation for momentum?

A

momentum = mass * velocity

60
Q

What is the unit for momentum?

A

kg m s^-1

61
Q

What is the principle of conservation of linear momentum?

A

momentum is always conserved in any interaction where forces act.
momentum before = momentum after

62
Q

How do force and momentum link?

A

force is the rate of change of momentum

F=change in momentum/change in time period

63
Q

Where does the weight act upon the object?

A

the centre of gravity

64
Q

What is the formula for work done (trig)?

A

W.d. = force * distance * cos θ

65
Q

What is gravitational potential energy?

A

the energy that an object has due to its position in a gravitational field

66
Q

What is power?

A

the rate of energy transfer

67
Q

What is an alternative formula for power?

A

Power = force * velocity

P = W/t
P = (Fd)/t
P = Fv

68
Q

What must always be true when using the SUVAT equations of motion?

A

The acceleration must be uniform - if the acceleration is changing, the equations are not valid.

69
Q

What does the gradient of a distance-time graph represent?

A

Speed

70
Q

What does the gradient of a displacement-time graph represent?

A

Velocity

71
Q

What does the gradient of a velocity-time graph represent?

A

Acceleration.

72
Q

Describe the shape of a velocity-time graph for an object travelling with uniform acceleration.

A

If acceleration is constant, the gradient of the velocity-time graph will be constant and so it will form a straight line graph.

73
Q

Describe the shape of a velocity-time graph for an object travelling with non-uniform acceleration.

A

If acceleration is not constant, the gradient of the velocity-time graph will change and so it will form a curve.

74
Q

Compare the velocity-time graphs for a uniformly accelerating and a uniformly decelerating object.

A

● For an accelerating object, the gradient will be positive
● For a decelerating object, the gradient will be negative

75
Q

Give five examples of scalar quantities.

A
  1. Distance
  2. Speed
  3. Mass
  4. Energy
  5. Temperature
76
Q

Give five examples of vector quantities.

A
  1. Displacement
  2. Velocity
  3. Acceleration
  4. Momentum
  5. Force
77
Q

How is a vector quantity represented on a diagram?

A

● As an arrow
● The direction of the arrow represents the direction of the quantity
● The length of the arrow represents the magnitude of the quantity

let's get physical! (20 decks)

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