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Physics > Physics Term 2 > Flashcards

Physics Term 2 Flashcards

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1
Q

How to improve reliability in a method?

A
  • Ensure 3 trials are done
  • Try to reduce subjective measurements by using the same person for each test, or using data loggers/equipment that removes making a judgement.
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2
Q

How to improve accuracy in a method?

A
  • Use equipment with the best possible limit of reading and minimal uncertainty so measured results are as accurate as possible.
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3
Q

How to improve the validity of a method?

A
  • Insure independent and dependent variables can be used to test the aim of the experiment.
  • Ensure all controlled variables are kept constant.
  • Make sure that there are at least 5 changes in the IV.
  • More controlled variables
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4
Q

How can you define reliability?

A

The consistency of results

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5
Q

How can you define accuracy?

A

How close do your measurements align with the true value.

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6
Q

How can you define validity?

A

Is the experiment measuring what is intended.

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7
Q

How to test if the results are reliable?

A
  • Percentage range of trial date. Less than 10% percentage range within all results show reliability.
    (Highest-Lowest / average) x 100
  • Low scatter of points within a graph.
  • Small error bars.
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8
Q

How to test if the results are accurate?

A
  • When a true value is provided, if the measured value is within 10% then it is accurate.
    (experimental-true value / true value) x 100
  • If the line of best fit passes through the origin.
    This only works if the two values have a 0,0 relationship.
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9
Q

How should you describe your IV?

A
  • State what you are changing
  • Explain what it is indicating of
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10
Q

How should you describe your DV?

A
  • The quantity you are measuring
  • How you are measuring it
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11
Q

How should you describe your CV?

A
  • Identify the variable.
  • Describe how you are going to control it.
  • Identify the value you are going to set it at.
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12
Q

How should you write your hypothesis?

A

Relate the IV to the DV. Example: As the IV (change made) the measured quantity (change observed) which indicates (effect of IV on DV)

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13
Q

What should be included in your risk assessment?

A
  • Identify: describe the risk
  • Assess: assess the possible consequences
  • Control: How will you take precautions to prevent it
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14
Q

What is the limit of reading

A
  • For any piece of equipment, the smallest increment it can measure is called the limit of reading and results should be measured to decimal place.
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15
Q

What is uncertainty

A
  • Uncertainty of measurement is a doubt we have in its magnitude. State the plus and minus margin that a measurement has.
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16
Q

How to measure uncertainty

A
  • With analogue instruments, the uncertainty is half the smallest value.
  • With digital instruments, the uncertainty is one unit of the smallest decimal place.
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17
Q

How to determine the gradient

A
  • Pick two points from the line of best fit. The two points should be as far away from each other as possible.
  • Draw a tringle using two dotted lines between the two points.
    Use the “rise/run” formula to calculate the gradient.
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18
Q

What units should you use for the line of best fit?

A
  • M on vertical and s on horizontal = m/s or ms(-1)
  • N on vertical and m on horizontal = N/m or Nm(-1)
  • kg on vertical and ms(-2) on horizontal = kg/ms(-2) or kg m(-1) s(-2)
19
Q

What are systematic errors

A
  • Same extent with each measurement
  • Problems with the measuring equipment
  • Can be reduced by calibrating instruments before use
20
Q

What are random errors

A
  • Occurs in any measurement as a result of variations
  • caused by unpredictable changes
  • Can be reduced through repetition
21
Q

What are vectors and scalars

A
  • Scalars are only described by a magnitude. (Time distance volume speed) To describe a scalar you need a magnitude and unit.
    Vectors are described by magnitude and direction. (displacement, velocity, force, acceleration) To describe vectors you must have magnitude, unit and direction.
22
Q

Difference between speed and velocity

A
  • Speed is the rate at which distance is travelled. Distance/time
  • Velocity is the rate at which displacement changes.
    displacement/time
23
Q

How to quickly convert from m/s to km/h

A
  • 1 m/s is 3.6 km/h
  • m/s to km/h (m/s x 3.6)
  • km/h to m/s (km/h / 3.6)
24
Q

How to determine displacement from velocity-time graph.

A
  • The area under the graph.
  • Area above the x-axis is one direction
  • Area under the x-axis in another
25
Q

What is acceleration?

A
  • Is the measure of the rates of change of velocity
  • acceleration involves the change in velocity
26
Q

v, u, a, t, s

A

v = final velocity
u = initial velocity
a = acceleration
t = time
s = displacement

27
Q

How to find the resultant of two vectors

A
  • Draw the first vector, and draw the second vector so that the head touches the tail. Draw an overall vector between the two.
  • Use pythag, or trig to find the resultant
28
Q

cosine and sine rule?

A
  • c* = a* + b* - 2ab cos C
  • a/sin A = b/sin b
29
Q

What is the normal force

A
  • The normal force acts perpendicular to the contact surface
30
Q

How to get the weight of an object

A

W = m x g
g = 9.8

31
Q

How are free-body diagrams drawn?

A
  • use the middle of the object from the tail.
  • force vectors show direction
  • show the net force using a dotted line that is clearly labelled.
32
Q

What is equilibrium

A

When the net force acting on an object is zero. It does not mean it is not in motion.

33
Q

Newtwons 1st law

A

An object in constant motion or at rest will remain in constant motion or at rest unless acted upon by an unbalanced external force.

34
Q

Newtons 2nd law

A

If there is a net force on an object it will undergo acceleration. F = ma

35
Q

Newtons 3rd law

A

Every action has an equal and opposite reaction.

36
Q

What is static friction and kinetic friction?

A
  • Static: This is the friction you need to overcome to start an object moving.
  • Kinetic: This is the friction present between to objects in relative motion
37
Q

What is inertia?

A

The tendency of an object to keep doing what it was doing

38
Q

What is momentum?

A

Momentum measures the inertia of moving objects.
p = mv
delta p / delta t = m x a

39
Q

what is the law of conservation of momentum?

A

In an isolated system, the total momentum of the system is conserved. Not only does the magnitude stay the same, but so does direction.
delta p (a) + delta p (b) = 0

40
Q

what is impulse?

A

Impulse is the change in momentum
delta p = F x t

41
Q

what is the formula for gravitational potential energy

A

Ug = mgh
Ug = gravitational potential energy (J)
m = mass of object (kg)
g = gravitational acceleration (ms-2)
h = height above the earth

42
Q

What is work?

A

When a force is exerted on an object and causes it to move.
W = F x s x cos(theta)

43
Q

What is power

A

Power is the rate at which work is done
P = work/delta time (watt)
P = F x v

44
Q

Energy time graphs

A
  • The slope is power
  • The area is work

Physics (4 decks)

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