Measurements

Question 1

Base quantities

Answer 1

• length
• mass
• time
• electric current
• temperature
• amount of substance

Question 2

Avagadro number

Answer 2

• one mole of any substance contains 6.02 x 10²³

Question 3

What is a homogenous equation

Answer 3

• is a equation where all the terms in the equation have the same units

Question 4

Homogenous equation and Physically correct equation

Answer 4

• physically correct equation is homogenous but a homogenous equation may not be physically correct

Question 5

Prefixes

Answer 5

• pico, nano, micro, milli, centi, deci
• tera, giga, mega, kilo, hecto, deca,

Question 6

What is a systemic error

Answer 6

• will result in all readings having a constant error in one direction

Question 7

What is a random error

Answer 7

• will result in a scatter of readings about a mean value

Question 8

How to reduce systemic error and random error

Answer 8

• eliminated by calibration curve and control experiments
• reduced by taking average of repeated readings

Question 9

What is accuracy

Answer 9

• degree to which a measurement approaches the true value of

Question 10

What is precision

Answer 10

• degree of agreement of repeated measurements of the same quantity

Question 11

Precision vs Accuracy

Answer 11

• small random error - small systematic error
• readings close to mean - mean close to true value

Question 12

Calculating uncertainty

Answer 12

• If y = kx + z, (U)y = k(U)x + (U)z
• If y = k(wx²/z³, (U)y/y = (U)w/w + 2(U)x/x + 3(U)z/z
• actual uncertainty to 1 s.f.

Question 13

What is scalar and vector

Answer 13

• quantity that has magnitude only, not direction
• quantity having both magnitude and direction