Length

Length is a dimesion of an object.

The length of a thing is the distance between its ends,

its linear extent as measured from end to end.

Ruler, or Meterstick

You should all be familiar with the use of a ruler or meter stick to measure small distances.

It is usually scaled off in centimeters, with smaller divisions of millimeters.

1. Measure the Length of the Middle finger and write it beside the finger, for all measurements go to the decimal.
2. Measure the Length of your hand and write it down
2. Measure the length of your book ? & write it down.
1. which is the length, whats the other side called?
2. Are all the measurements from the class the same?
3. Measure the Height, width and length of the desk

When using these pieces of equipment, it is very important to look directly above the measuring point to overcome the error of parallax

What could you use to measure the size of your head ?

Measuring tape

a handy way to measure long distances

Opisometer

Meaning and Definition

(n.) An instrument with a revolving wheel for measuring a curved line, as on a map.

An opisometer has a little wheel that is on a screw.

• The wheel is rolled to one side of the screw to begin with.
• The wheel is then rolled along the curved line until it reaches the end of the curved line.
• To find out how long the curved line is we roll the wheel backwards beside a ruler or meter stick, starting at the zero.
• The distance that the wheel rolls back along the ruler is the length of the curved line.

Draw a short curvy line find the length of it, write the length of the curvy line down beside the line.

What if the curved line is longer than the ruler, what would you do?

Draw a longer curvey line

What if the curved line is longer than the screw distance, what would you do?

Trundle wheel

This wheel measures one meter on its circumference, i.e. if you roll it along, 1 full rotation will take the wheel 1 meter.

This is used for measuring distance that are too long for a meter stick to be useful, eg the length of a football field. A calipers is a device used to measure the distance between two symmetrically opposing sides.

A caliper can be as simple as a compass with inward or outward-facing points.

The tips of the caliper are adjusted to fit across the points to be measured, the caliper is then removed and the distance read by measuring between the tips with a measuring tool, such as a ruler.

So a Calipers does not directly measure the distance but can be used indirectly in conjunction with another device.

Using the calipers to measure

1. Inner Width of a testtube ___ cm
2. Outside of a graduated cylinder ___ cm
3. The thickness of the glass in a gas Jar ___ cm
4. The thickness of your science book ___cm
5. the Thickness of the desk ___ cm
6. the width of a chair leg ___ cm
7. the width of my hand ___ cm
8. The thickness of a pen ___ cm
9. the diameter of the lab taps ___ cm

A Vernier Calipers

A vernier calipers is a very accurate way to measure distances or thicknesses of small objects.

Photo needed !!

for details on how to use the verier scale it follow the link below.

http://surendranath.tripod.com/Applets/General/Vernier/Vernier.html

Could you measure the thickness of one sheet of paper ?

Is there more than one way?

Measure the thickness of a number of pages

Use a Calculator to divide the thickness (in cm) by by the number of pages

Write down the thickness as ________cm there maybe a lot of digits !

Light !!

The Distance from the earth to the moon is of considerable interest to scientists (and people living by the sea. To that end, or for that reason NASA left a prism mirror on the Moon when they set up the Apollo lunar surface experiment package, back in the early 70's. The 1st landing on the moon was in 1969. Since then a laser is shone at a partcular point on the moon, it bounces back from a corner reflector (basically a prism) and the time taken for it to return is measured. Then scientists can determine how far away the moon is to the nearest centimeter!

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