Working as a Physicist

Question 1

The principle of ‘homogeneity of units’ means:

Answer 1

Units in any equation must be the same on both sides

Question 2

State the SI base quantities.

Answer 2

Amount of Substance
Current
Distance
Luminocity
Mass
Temperature
Time

Question 3

State the SI base units.

Answer 3

Moles (mol)
Amperes (A)
Meters (m)
Candela (cd)
Kilograms (kg)
Kelvin (K)
Seconds (s)

Question 4

The SI derived unit for momentum is:

Answer 4

kg m s⁻¹

Question 5

A quantity that has the SI derived unit s⁻¹ is:

Answer 5

Frequency

Question 6

A quantity that has the SI derived unit kgm⁻³ is:

Answer 6

Density

Question 7

What are the following conversions?

pN→ nN → μN → mN → N → kN → MN → GN → TN

Answer 7

p x10⁻¹²
n x10⁻⁹
μ x10⁻⁶
m x10⁻³
-
k x10³
M x10⁶
G x10⁹
T x10¹²

Question 8

The units for strain are:

Answer 8

No units

Question 9

A graph with the current on the y-axis and time on the x-axis shows?

Answer 9

The current against time

Question 10

What does the gradient of a velocity-time graph represent?

Answer 10

Acceleration

∵gradient = Δy / Δx
& velocity (ms⁻¹) / time (s) = acceleration (ms⁻²)

Question 11

What is the dependent variable on a graph?

Answer 11

y-axis

Question 12

What is the independent variable on a graph?

Answer 12

x-axis

Question 13

What does the area under a force-displacement graph represent?

Answer 13

Work Done

∵area = Δy x Δx
& Force x Displacement = Work Done

Question 14

Why do we have base units?

Answer 14

These provide a source to derive all other units and ensure that research can be easily compared.

Question 15

What is absolute uncertainty?

Answer 15

The uncertainty in a specific measurement

Question 16

What is the unit for absolute uncertainty?

Answer 16

It is given in the same units as the original measurement

Question 17

How is the absolute uncertainty stated?

Answer 17

It is stated after the measurement as ± [number] [unit].

Question 18

What are three ways to calculate absolute uncertainty?

Answer 18

• half the smallest division on the instrument.
• half of the last significant figure recorded.
• half the range of your repeats.

Question 19

What is % uncertainty?

Answer 19

It’s how the size of the uncertainty compares to the measurement.

Question 20

How is the % uncertainty stated?

Answer 20

It is stated after the measurement as ± [number] %

Question 21

How do you calculate % uncertainty?

Answer 21

(the absolute uncertainty / by the average measurement) x 100

Question 22

What happens to the uncertainty when you:

1) add/subtract measurements?
2) multiply/divide measurements?
3) raising measurements to a power?

Answer 22

1) add the absolute uncertainties.
2) add the percentage uncertainties.
3) multiply the percentage uncertainty by the power.