Paper 3a

Question 1

How to ensure that measurements from a micrometer are not affected by systematic error?

Answer 1

• Close jaws using ratchet
• Confirm that instrument reads zero

Question 2

What is the horizontal/vertical bar in the middle of an oscilloscope called?

Answer 2

central horizontal/vertical graduation

Question 3

If emf increases, what settings on oscilloscope should be changed?

Answer 3

Adjust Y-voltage gain to a less sensitive setting, to increase the number of volts/div

Question 4

Explain where you should put a fiducial marker in a pendulum setup

Answer 4

Below the bob’s equilibrium position, as this is where the bob moves the fastest, so this is where the transit time is least

Question 5

If log y varies linearly with log x, what is the relationship between x and y?

Answer 5

• They are linked by the power law
• ( y∝xⁿ )

Question 6

How should you read the volume in a measuring cylinder?

Answer 6

By reading from the bottom of the meniscus at eye level

Question 7

Uncertainty in reading

Answer 7

​± half the smallest division

Question 8

Uncertainty in measurement

Answer 8

±1 smallest division

Question 9

Uncertainty in digital reading

Answer 9

± the last significant digit​

Question 10

How to reduce uncertainty in measuring a length?

Answer 10

• Fix one end of ruler
• As only the uncertainty in one reading is included

Question 11

What is the rule for significant figures when taking logarithms?

Answer 11

num. of significant figures in data → num. of decimal places in log

Question 12

Axis title for ln(x) where x is in cm

Answer 12

ln( x/cm )

Question 13

Axis title for x² where x is in cm

Answer 13

(x/cm)²

Question 14

Biggest thing you can measure in micrometer

Answer 14

50mm

Question 15

What to use to measure a 10mm diameter hole

Answer 15

Vernier callipers
(micrometers only measured outside diameters)

Question 16

What is the cause of parallax error?

Answer 16

Viewing the object against the scale from an angle that is not perpendicular to the scale

Question 17

Uncertainty in values in the data sheet

Answer 17

± the last significant digit​

Question 18

How many data points is sufficient to plot: a straight line? a curve?

Answer 18

straight line → 6-8 data points
curve → 10+ data points

Question 19

5 reasons to plot a graph

Answer 19

• To compare the data against a formulae or relationship
• To ameliorate the effect of random errors using the gradient of the best fit line
• To ameliorate the effect of systematic errors using the gradient
• To identify random error through the spread of data about the best fit line
• To identify systematic error through the intercepts on the graph

Question 20

Apparatus for measuring pressure

Answer 20

Pressure gauge

Question 21

Apparatus for measuring force

Answer 21

Newton-meter

Question 22

Name a way to measure the time of a moving thing with less uncertainty than a stopwatch

Answer 22

Light gates

Question 23

How to get something exactly vertical

Answer 23

Use a plumb line (to set or measure the vertical)

Question 24

2 ways to reduce systematic error in radiation counts

Answer 24

• Remove all other radioactive sources from the room
• Take all measurements on the same day

Question 25

Why would you put a mirror behind a scale of an analogue meter?

Answer 25

* So that the needle hides its own reflection * To reduce/eliminate parallax