Logs

Question 1

True or False

Logarithm have units.

Answer 1

• False.
• Logarithms DO NOT have units BUT, you should include ORIGINAL units for what you did “log” to in the table.

Question 2

2^n = 50
How would I work out what 9 is using log?

Answer 2

log both sides of equation.
nlog (2) = log (50)
log(50)/ log (2) = n
n = 5.64

Question 3

I logged time in seconds to give log values. How would I display these units in a table?

Answer 3

Log (time/s)

Question 4

When do we use log scales?

Answer 4

• When values obtained from experiment have VERY LARGE RANGE.
• Allows us to compare VERY LARGE values to very small values easily.

Question 5

Why would we use log scaled on graphs?

Answer 5

• Range = too large.
• Important so you can read both small + large values on graph.
• Graph would be v. difficult to read without log.

Question 6

What is issue with not using log graphs when there is a LARGE range of data?

Answer 6

• Makes very small values look like they are at 0 on graph.

Question 7

I have a log value of 7.55 for number of bacteria at an antibiotic conc. of 25%.
Work out the NUMBER of bacteria that grew at this concentration.

Answer 7

10⁷⋅⁵⁵ = 35481338.92