Module 2

Question 1

Find standard form for: Pico

Answer 1

10^-12

Question 2

Find standard form for: Nano

Answer 2

10^-9

Question 3

Find standard form for: Micro

Answer 3

10^-6

Question 4

Find standard form for: Milli

Answer 4

10^-3

Question 5

Find standard form for: Centi

Answer 5

10^-2

Question 6

Find standard form for: Deci

Answer 6

10^-1

Question 7

Find standard form for: Kilo

Answer 7

10^3

Question 8

Find standard form for: Mega

Answer 8

10^6

Question 9

Find standard form for: Giga

Answer 9

10^9

Question 10

Find standard form for: Tera

Answer 10

10^12

Question 11

What is the SI unit for: Luminous Intensity

Answer 11

Candela (cd)

Question 12

What is the SI unit for: Amount of substance

Answer 12

Mole (mol)

Question 13

What does it mean for an equation to be homogeneous?

Answer 13

It means that all the terms in the equation have the same units.

Question 14

Use units to show that the equation v = u + at is homogeneous.

Answer 14

v and u are both velocities, with base units ms^-1

at is acceleration x time, so ms^-2 X s = ms^-1

The units of all three terms in the equaton are ms^-1, so the equation is homogeneous.

Question 15

What is an error?

Answer 15

The difference between a measured value and the true or theoretically correct one.

Question 16

What is a random error?

Answer 16

Unpredictable variation between measurements that leads to a spread of values about the true value. (above and below the true value)

Question 17

How can random error be reduced?

Answer 17

By taking repeat measurements.

Question 18

What do systematic errors cause?

Answer 18

Causes all readings to differ from the true value by a fixed amount.

It tends to shift all measurements in the same direction.

Question 19

Could repeat readings be used to reduce systematic error?

Answer 19

No. Systematic error cannot be corrected by repeat readings, instead a different technique or apparatus should be used.

Question 20

What is a zero error?

What does it result in?

Answer 20

A form of systematic error, caused when a measuring instrument is not properly calibrated or adjusted, giving a non-zero value when the true value is zero.

This results in all measurements being offset by a fixed amount.

Question 21

What is a parallax error?

Answer 21

An error caused by reading a scale at the wrong angle.

Question 22

Give an example of a parallax error.

Answer 22

When your eye is not parallel with the meniscus when using a measuring cylinder.

Question 23

Give an example of a random error.

Answer 23

Variable heating in circuits causing variations in the current being measured.

OR

An unexpectedly large extension of a metal wire, due to a fault in its structure.

Question 24

What is a systematic error?

Answer 24

An error introduced by an inaccuracy in the apparatus or its use by the person conducting the investigation.

Question 25

Give an example of a systematic error.

Answer 25

The scale printed on a metre ruler is incorrect and the ruler scale is only 99.0cm long.

Question 26

Define precision.

Answer 26

A measure of how close a measurement is to the mean value. It only gives an indication of the magnitude or random errors, not how close data is to the true value. The smaller the spread of values, the higher the precision.

Question 27

Define accuracy.

Answer 27

A measure of how close a measurement is to the true value.

Question 28

What combinations of precision and accuracy can you have?

Answer 28

A value can have poor accuracy and poor precision. A value can have poor accuracy but good precision. A value can have good accuracy and good precision.

Question 29

How do systematic errors affect precision and accuracy?

Answer 29

Accuracy is affected by any systematic errors that are not accounted for, as the systematic error takes the measured value away from its true value. Precision, which is ultimately determined by the resolution of the apparatus being used, remains unaffected.

Question 30

What is the absolute uncertainty of a measurement?

Answer 30

It shows how large the uncertainty actually is, and has the same units as the quantity being measured.

Question 31

What is percentage uncertainty?

Answer 31

The absolute uncertainty divided by the measured value, expressed as a percentage.

Question 32

The diameter of a ball is 63mm. A metre ruler with centimetre and millimetre graduations was used. What is the absolute uncertainty?

Answer 32

+- 0.5mm So the diameter of the ball could be expressed as 63 +- 0.5mm

Question 33

How do you determine the uncertainty involving the use of a stopwatch (precise to 0.01s)?

Answer 33

Use the uncertainty of reaction time (about 0.5s) when stating a time value and its absolute uncertainty. This is done because human reaction times are not as quick as 0.01s.