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AS Physics > Definitions 1 > Flashcards

Definitions 1 Flashcards

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1
Q

Homogenous units

A

When each term has the same base units, the equation is said to be homogenous or ‘balanced’

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2
Q

Scalar

A

A quantity that has a magnitude/size

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3
Q

Vector

A

A quantity that has a magnitude/size and direction

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4
Q

Accuracy

A

How close a reading is to its true value

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5
Q

Precision

A

Smallest change in value that can be measured by an instrument

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6
Q

Random errors

A

An uncontrollable error that changes with each reading of a measurement caused by unknown and unpredictable changes

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7
Q

Systematic errors

A

An error caused by the imperfection of the instrument used causing readings to differ from the true value by a consistent amount each time a reading is made

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8
Q

Uncertainty

A

The range of values within which a measurement is likely to be in

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9
Q

Acceleration

A

The rate of change of velocity

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10
Q

Displacement

A

The straight line distance between a start and finish point in a specific direction

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11
Q

Distance

A

The total length travelled by an object

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12
Q

Speed

A

The distance travelled per unit time

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13
Q

Terminal velocity

A

The maximum constant velocity achieved by an object in free fall when the resultant force is zero

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14
Q

Velocity

A

A vector equal to the rate of change of displacement

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15
Q

Conservation of momentum

A

Total momentum of an isolated system of interacting bodies remains constant, provided there are no external resultant forces acting

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16
Q

Elastic collisions

A
  1. Total momentum and total kinetic energy of a system is conserved
  2. Relative speed of approach is equal to the relative speed of separation: u1-u2 = v2-v1
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17
Q

Force

A

The rate of change of momentum of a body

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18
Q

Impulse

A

The product of a force and the time during which the force is applied

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19
Q

Inelastic collisions

A
  1. Total momentum of a system is conserved.
  2. But total kinetic energy is not conserved and relative speed before impact is not equal to relative speed after impact
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20
Q

Linear momentum

A

The product of an objects mass and velocity

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21
Q

Mass

A

The measure of inertia of a body or the property of a body that resists change in motion

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22
Q

Newton’s 1st law

A

A body remains at rest or constant velocity unless acted on by a resultant force

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23
Q

Newton’s 2nd law

A

The resultant force is proportional to the rate of change of momentum

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24
Q

Newton’s 3rd law

A

If one body exerts a force on another, it will experience a force by the other body, which is equal in magnitude and opposite in direction

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25
Q

Weight

A

The downward force due to the gravitational field

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26
Q

Centre of gravity

A

The point on an object at which the entire weight of the body appears to act

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27
Q

Density

A

The amount of mass per unit volume of a substance

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28
Q

Equilibrium

A
  1. Resultant force is zero in all directions
  2. Sum of clockwise moments = sum of anticlockwise moments
29
Q

Moment/torque

A

The product of the force and the perpendicular distance to the force from the pivot to the line of action of the force

30
Q

Pressure

A

The perpendicular or normal force applied per unit area

31
Q

Principle of moments

A

The sum of the clockwise moments about a point equals the sum of the anticlockwise moments about the same point

32
Q

Couple

A

A pair of forces that act to produce rotation called torque

33
Q

Energy

A

The ability to do work

34
Q

Work done

A

The product of a force and the distance moved in the direction of the force

35
Q

Gravitational potential energy

A

Energy stored due to the height or position of a mass in a gravitational field

36
Q

Kinetic energy

A

Energy of an object due to its motion

37
Q

Power

A

The work done or energy transferred per unit time

38
Q

What are the 7 SI base quantities?

A

Mass, length, time, current, temperature, amount of substance, luminous intensity

39
Q

What are the 7 SI base units?

A

Kilogram, meter, second, ampere, kelvin, mole, candela

40
Q

What causes terminal velocity?

A
  1. Air resistance acts on the object while it is free falling
  2. The drag forces increase as the object keeps falling, causing the resultant force to decrease
  3. Eventually, the drag forces will equal the weight force and the resultant force will equal zero
  4. Because the resultant force is zero, there is no acceleration and the velocity of the object becomes constant
41
Q

Hydrostatic pressure

A

The pressure exerted by a fluid on an object in equilibrium at a given point within the fluid due to the force of gravity

42
Q

The value of atmospheric pressure

A

101kPa

43
Q

Archimedes law

A

When an object submerged in a fluid is at rest, meaning it has an upward buoyancy upthrust force equal to the weight of the fluid displaced by the object

44
Q

Equation for upthrust

A

F = pgV

p = density of fluid
V = volume of fluid displaced
g = acceleration due to gravity

45
Q

What is the upthrust equal to when an object is in equilibrium?

A

When an object is at equilibrium and is stationary in a fluid then the upthrust of the object = the weight of the object + any other downward forces

46
Q

In what direction does tension act?

A

Tension acts away from the object it is acting or pulling on

47
Q

Upthrust

A

The upward resultant force acting on an object submerged in a fluid that is due to the difference in hydrostatic pressure at the top and bottom of the object

48
Q

How to do you convert from m to some other prefix?

A

Divide by the prefix you want, e.g. 5m → nm = 5 ÷ 10^-9

49
Q

How many significant figures should you write uncertainties to?

A
  1. Always give the uncertainty to the same sf as all the other uncertainties given
  2. For percentage uncertainties the uncertainty should be given to 2sf
50
Q

Equation relating work to energy

A

Work = ∆E
W = ∆EK ∆GPE = ∆EP

51
Q

What happens if all EK is transferred to GPE or EP?

A
  1. ∆EK = ∆GPE
  2. ∆EK = ∆EP
52
Q

How do you calculate work done against resistive force?

A

W resistive = W - ∆EK

53
Q

How do you calculate the total resistive forces acting on an object?

A

F net = mg - F resistive
F net = sum forces in the direction of motion - sum forces opposing the motion in the opposite direction of motion

54
Q

How do you remedy a systematic error?

A
  1. Look to see if there is a zero error and if there is subtract it from all readings
  2. Use new/different instruments
55
Q

How do you remedy a random error?

A

Take many readings and find the average of the readings

56
Q

List all the scalar quantities:

A

Distance, speed, mass, time, energy, volume, density, pressure, electric charge, temperature

57
Q

List all the vector quantities:

A

Displacement, velocity, acceleration, force, momentum

58
Q

What are the conditions for Newton’s 3rd law?

A
  1. Both forces are of the same kind
  2. The forces must act on different objects
59
Q

How do you know if vectors arrows are in equilibrium?

A

If the vector arrows are ‘closed’ and all the arrow heads are continuous in one direction then there is no resultant force

60
Q

Equation for the torque of a couple:

A

Moment of a couple = one of the forces * the perpendicular distance between the two forces

61
Q

What are the conditions for a couple?

A
  1. The forces must be equal to magnitude, opposite in direction
  2. The forces must be perpendicular to the distance between them
  3. The forces cannot share the same line of action
  4. Couples produce a resultant force of zero, therefore, the object rotating does not accelerate
62
Q

What is the triangle method for combining vectors?

A
  1. Link the vectors head-to-tail
  2. The resultant vector is formed by connecting the tail of the first vector to the head of the second vector
63
Q

What is the equation method for combining vectors?

A

When two or more vectors are added together or one is subtracted from another, a single resultant vector is formed

  1. if X + Y = Z, then the arrow heads of vectors X and Y are in the same direction
  2. Hence, if X = Z - Y, then the arrow heads of vectors Z and Y are heading away from each other
64
Q

What is the parallelogram method for combining vectors?

A
  1. Link the vectors tail-to-tail
  2. Complete the resulting parallelogram
  3. The resultant vector is the diagonal of the parallelogram
65
Q

What are coplanar forces?

A

Coplanar forces are forces that act in the same plane

66
Q

How does the magnitude of the horizontal component of a vector change?

A

It changes with a cosine curve

67
Q

How does the magnitude of the vertical component of a vector change?

A

It changes with a sine curve

68
Q

What does precision depend on?

A

Precision depends on the number of significant figures or decimal places a quantity is given to

AS Physics (3 decks)

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