Measuring means finding a number that describes the size of something. In particular, we determine the duration between two events by measuring the time between those events. We use time units for this purpose.
The most popular measurement system within the scientific community is the metric system. Within the metric system, the most common units of measurement are called base units.
The base unit for time is the second, which we denote using the symbol "" We measure the time between two events using clocks like the ones shown below.
We use milliseconds to measure smaller time intervals. The symbol for milliseconds is "" The prefix stands for milli, which means Therefore, equals
Notice that if we add to itself times, we get exactly
Therefore, equals as stated in the diagram.
One millisecond is a very short time interval. To put this into context, a single blink of a human eye is around milliseconds on average.
Suppose we want to measure the duration of the collision between two billiard balls. Which metric unit could we use?
A table showing the metric units of time is given below.
| Name | Symbol |
|---|---|
| Second | |
| Millisecond |
Therefore, from the given options, the only unit of time is
An electrical impulse has a time duration of $1\,\textrm{s}.$ What is this time in milliseconds?
|
a
|
$1\,000\,\textrm{ms}$ |
|
b
|
$100\,\textrm{ms}$ |
|
c
|
$0.1\,\textrm{ms}$ |
|
d
|
$10\,\textrm{ms}$ |
|
e
|
$0.01\,\textrm{ms}$ |
Suppose we want to measure the time duration of a lightning strike. Which metric unit could we use?
|
a
|
$\textrm{m}$ |
|
b
|
$\textrm{ms}$ |
|
c
|
$\textrm{g}$ |
|
d
|
$\textrm{km}$ |
|
e
|
$\textrm{mg}$ |
Other time units in common usage are minute, hour, day, and week.
A table showing our units of time is given below.
| Name | Symbol | Conversion |
|---|---|---|
| Second | ||
| Minute | ||
| Hour | ||
| Day | ||
| Week |
A fitness class lasts exactly What is this time in minutes?
A table showing the units of time is given below.
| Name | Symbol | Conversion |
|---|---|---|
| Second | ||
| Minute | ||
| Hour | ||
| Day | ||
| Week |
Therefore, is equivalent to
A journey between two locations lasts exactly $1\,\textrm{day}.$ What is this time in hours?
|
a
|
$100\,\textrm{h}$ |
|
b
|
$60\,\textrm{h}$ |
|
c
|
$24\,\textrm{h}$ |
|
d
|
$7\,\textrm{h}$ |
|
e
|
$10\,\textrm{h}$ |
A film festival lasts exactly $1\,\textrm{week}.$ What is this time in days?
|
a
|
$12\,\textrm{days}$ |
|
b
|
$7\,\textrm{days}$ |
|
c
|
$8\,\textrm{days}$ |
|
d
|
$5\,\textrm{days}$ |
|
e
|
$6\,\textrm{days}$ |