Module 2 Chapter 1 Physical Quantities, Units and Measurements

Question 1

Unit for Acceleration

Answer 1

m s-2

metres per second squared

Question 2

Unit for Density

Answer 2

kg m-3

kilograms per cubic metre

Question 3

Unit for Electrical Charge

Answer 3

C

coulomb

Question 4

Unit for Energy

Answer 4

J

joule

Question 5

Unit for Force

Answer 5

N

newton

Question 6

Unit for Momentum

Answer 6

kg m s-1

kilogram metres per second

Question 7

Unit for Potential Difference

Answer 7

V

volt

Question 8

Unit for Power

Answer 8

W

watt

Question 9

Unit for Pressure

Answer 9

Pa

pascal

Question 10

Unit for Velocity

Answer 10

m s-1

metres per second

Question 11

Prefix: pico

Answer 11

p

10^-12

Question 12

Prefix: nano

Answer 12

n

10^-9

Question 13

Prefix: micro

Answer 13

µ

10^-6

Question 14

Prefix: milli

Answer 14

m

10^-3

Question 15

Prefix: centi

Answer 15

c

10^-2

Question 16

Prefix: kilo

Answer 16

k

10^3

Question 17

Prefix: mega

Answer 17

M

10^6

Question 18

Prefix: giga

Answer 18

G

10^9

Question 19

Prefix: tera

Answer 19

T

10^12

Question 20

SI Unit for Mass

Answer 20

kg

Kilogram

Question 21

SI Unit for Length

Answer 21

m

Metre

Question 22

SI Unit for Time

Answer 22

s

Second

Question 23

SI Unit for Temperature

Answer 23

K

Kelvin

Question 24

SI Unit for Electrical Current

Answer 24

A

Ampere

Question 25

SI Unit for Amount of Substance

Answer 25

mol

Mole

Question 26

SI Unit for Luminous Intensity

Answer 26

cd

Candela

Question 27

Examples of Random Errors

Answer 27

• Variable heating in circuits causing variations in the current being measured
• An unexpected large extension of a metal wire due to a fault in its structure

Question 28

Examples of Systematic Errors

Answer 28

• Using a ruler with a fault in the measurements printed on it
• A parallax error caused by reading a scale at the wrong angle

Question 29

What do random errors reduce?

Answer 29

Precision

Question 30

What do systematic errors reduce?

Answer 30

Accuracy

Question 31

Percentage Uncertainty

Answer 31

(uncertainty/measured value) * 100

Question 32

How can one measure uncertainty?

Answer 32

By using one of two methods:

• Calculating a % difference between your ‘best’ and ‘worst’ lines of best fit
• Combining your uncertainties for each of your measurements (either summing or multiplying them depending on how you use the values)

Question 33

For y = ab, how would you find the uncertainty of y, given the uncertainties of a and b?

Answer 33

% uncertainty in y = % uncertainty in a + % uncertainty in b

Question 34

For y = a/b, how would you find the uncertainty of y, given the uncertainties of a and b?

Answer 34

% uncertainty in y = % uncertainty in a + % uncertainty in b

Question 35

For y = a^n, how would you find the uncertainty of y, given the uncertainty of a?

Answer 35

% uncertainty in y = (% uncertainty in a) * n

Question 36

For y = a ± b, how would you find the uncertainty of y, given the uncertainties of a and b?

Answer 36

absolute uncertainty of y = absolute uncertainty of a + absolute uncertainty of b