Science Skills

Question 1

uncertainty

Answer 1

An estimate of the range of values where the true value lies

Question 2

absolute uncertainty

Answer 2

How high above or below a measurement can be from the true value; the amount by which the value is uncertain

Question 3

if a is a measurement, what is Δa?

Answer 3

The absolute uncertainty of a

Question 4

precision of a measuring instrument = ?

Answer 4

its resolution

Question 5

precision of lots of measurements = ?

Answer 5

the range of the values

Question 6

difference between a reading and a measurement (+ example)

Answer 6

Reading = 1 measured value e.g. mass
Measurement = 2 measured values e.g. length

Question 7

formula for absolute uncertainty for a:
a) reading
b) measurement

Answer 7

a) ± half of resolution
b) resolution

Question 8

formula for absolute uncertainty for lots of readings e.g. when you’ve taken repeats

Answer 8

± range / 2

need to check

Question 9

formula for absolute uncertainty for a mean

Answer 9

± range / 2

Question 10

What absolute uncertainty are human-recorded time measurements limited to? Why?

Answer 10

Time is limited to an absolute uncertainty of ± 0.2-0.5s due to human error

Question 11

A force is measured to be 2N. What is the uncertainty?

Answer 11

1 / 2 = ± 0.5

Question 12

How is the percentage uncertainty determined from a single reading whose value is a?

Answer 12

absolute uncertainty / measured value (a) × 100 = εa

epsilon a = percentage uncertainty

need to check

Question 13

How can you calculate the fractional uncertainty?

Answer 13

absolute uncertainty / measured value

Question 14

Combining
uncertainties should
always make the
uncertainty ____.

Answer 14

increase

Question 15

When adding or subtracting data with uncertainties, how do you calculate the absolute uncertainty?

Answer 15

Add the absolute uncertainties

Question 16

When multiplying or dividing data with uncertainties, how do you calculate the uncertainty?

check this FC

Answer 16

Add the percentage uncertainties - this gives you a percentage uncertainty e.g. ± 9.25%

Question 17

When raising data with an uncertainty to a power, how do you calculate the uncertainty?

Answer 17

Multiply the percentage uncertainty by that power (i.e. you’re adding the uncertainty that many times)

Question 18

When multiplying data with an uncertainty by a constant, how do you calculate the a) absolute uncertainty and b) the percentage uncertainty?

Answer 18

a) multiply the absolute uncertainty by that constant
b) you don’t multiply the percentage uncertainty by the constant (it stays the same???).

not really sure how the percentage uncertainty changes

Question 19

What are the two different instruments that you can use to measure length more accurately?

Answer 19

• Caliper (can measure internal & external widths) - resolution of 0.1mm
• Micrometer (used in class, has two measuring cylinder things) - resolution of 0.01mm

Question 20

What are the two different instruments that you can use to measure mass more accurately?

Answer 20

• Spring balance (like in shops for measuring the mass of fruit) - resolution of 0.1g
• Top-pan balance - resolution of 0.01g

Question 21

How many decimal places should you quote errors to?

Answer 21

1 or 2 d.p.s

Question 22

How many decimal places should you quote results to?

Answer 22

The same number of d.p.s as the error

Question 23

Neville measures the diameter of a metal block to be 32.67 ± 0.1mm. Is this ok? Explain your answer.

Answer 23

No - it should be 32.7 ± 0.1mm as results & errors should be written to the same power e.g. 10^-2

Question 24

Liliana is drawing a table. In a column for temperature, she has 8.5°C, 9.7°C, 10.3°C and 12.0°C. Is this ok? Explain your answer.

Answer 24

Yes - when changing from one power of 10 to another in a table column, keep the number of d.p.s the same to not change the accuracy of the results