2 - Foundations of Physics

Question 1

What is a quantity?

Answer 1

A property of an object or phenomenon that can be measured.

Question 2

What are the 6 (total 7) SI base quantities/units that you need to know?

Answer 2

length, mass, time, electric current, temperature, amount of a substance, (light intensity)

Question 3

What is the unit and symbol for distance?

Answer 3

metre, m

Question 4

What is the unit and symbol for mass?

Answer 4

kilogram, kg

Question 5

What is the unit and symbol for time?

Answer 5

second, s

Question 6

What is the unit and symbol for electric current?

Answer 6

ampere, A

Question 7

What is the unit and symbol for temperature?

Answer 7

kelvin, K

Question 8

What is the unit and symbol for amount of a substance?

Answer 8

mole, mol

Question 9

Why is a unit symbol sometimes written in upper case?

Answer 9

Because it was named after a person (but the unit name is always lower case)

Question 10

What do we use to measure quantities other than the 7 base quantities?

Answer 10

Derived units

Question 11

How do we work out derived units?

Answer 11

From the base units and the equations which relate the derived quantities to the base quantities.

Question 12

What is a scalar quantity?

Answer 12

A quantity with magnitude but no direction.

Question 13

What is a vector quantity?

Answer 13

A quantity with magnitude and direction.

Question 14

What does it mean if an equation is homogeneous?

Answer 14

Both sides of the equation have the same SI units.

Question 15

What is an uncertainty?

Answer 15

How sure we can be about a measurement.

Question 16

What do you do when you take multiple measurements?

Answer 16

Find the average to find the actual value.

Question 17

What is the absolute uncertainty?

Answer 17

Half of the range.

Question 18

How do you work out an uncertainty?

Answer 18

Find the average. Then find half of the range.

AVG+-HALF RANGE

Question 19

How do you work out a percentage uncertainty?

Answer 19

Find the average. Find out half of the range as a percentage of the average.

AVG+- (HALF RANGE / AVG x 100)

Question 20

What is a true value?

Answer 20

A value that would be obtained in an ideal measurement. The values that you expect to get in an experiment.

Question 21

What is a random error and what causes them?

Answer 21

A measurement error which varies unpredictibly. They can occur due to factors that are not controlled in the experiment / difficulty in reading the measurement device.

Question 22

What is a systematic error and what causes them?

Answer 22

A measurement error in which the measurement differs from the true value by the same amount each time. They can occur due to the way measurements are taken / faulty measuring devices.

Question 23

Give a difference between a random error and a systematic error.

Answer 23

Systematic errors can be corrected.

Question 24

What do you do to the uncertainty when you add or subtract two quantities?

Answer 24

Add the absolute uncertainties.

Question 25

What do you do to the uncertainty when you multiply or divide two quantities?

Answer 25

Add the percentage uncertainties.

Question 26

What do you do to the uncertainty when you raise a quantity to a power (n)?

Answer 26

Multiply the uncertainty by (n).

Question 27

How do you calculate vectors in a straight line?

Answer 27

Add or subtract (depending on direction)

Question 28

How do you calculate perpendicular vectors?

Answer 28

Use Pythagoras theorem.

Question 29

What steps do you follow to solve vector problems?

Answer 29

1. Break down into horizontal and vertical components
2. Add/subtract all parallel vectors
3. Use Pythagoras to work out the resultant force.