# Measurement of length

A length can something be measured by using meter rule, caliper, venire caliper, and micro screw gauge. The instrument for measurement of length depends on how large or small the length is. If the length is very long like foot ball field, you use tape; a shorter distance like your reading table can be measured using meter rule. A cylindrical object can be measured using calipers and meter rule

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## How to us Venire calipers

We use venire caliper to measure internal diameter of a TUBE, the depth of a cavity or the thickness of a plate, that which cannot be measured by the caliper and meter rule. Venire caliper can measure to an accuracy of 0.01cm or o.1mm.

The venire caliper has tow scales, main scale M, and venire scale V, the venire scale which is smaller, is added to main scale to give the fraction of the smallest division on the scale.

The main scale is calibrated in millimeter, while the venire is obtained by dividing nine of 0.1cm into ten equal intervals, so that each venire division has 0.09cm.

When you measure with venire caliper , take your read at where the main and venire scale coincide, so take the reading of main and venire scale respectively, then add them together and that gives you the actual reading. For example if the reading in the main and venire are 4.3cm and 0.07cm respectively, this means that the actual reading is 4.3 + 0.07= 4.37cm.

## How to us micro meter screw gauge

If you want to measure something like diameter of a wire, diameter of small ball or thickness of a paper, you use micro screw gauge for your accuracy measurements.

Micro screw gauge measure to accuracy of 0.01millimeter. Like venire caliper it has main scale and venire scale. The main scale is graduated in millimeter, while venire, with circular venire V contains 50 divisions. To take your reading from micro screw gauge, you first take the reading in main scale and the one in venire scale. After that you add the both reading together.

For example, if you have 4.00mm in the main scale and 0.11mm in the venire scale, you add them together to get the actual reading.

Ie 4.00 + 0.11 =4.11mm.

The result follow from the fact that 50 divisions of venire V, correspond to 0.5mm of main scale

- 1 division of v = 01mm M
- 11 divisions of V = 0.11 mm of M.

## Measurement of Time

We can measure time in laboratory using stop watch or stop clock. Stop watch can measure to an accuracy of 0.1 second while stop clock measure time to accuracy of 0.2 seconds.

But today we have quartz clocks and atomic clocks that can measure more accurately than stop watches or stop clocks

### Measurement of mass

Mass of a body is the quantity of the matter it contains while the weight of a body is the force of gravity on it.

Mass is measured by comparing it with the standard masses using balance. So mass can be measured using** beam balance or chemical balance.**

**Chemical balance** measure to accuracy of 0.001grom and 1gram depending on its sensitivity. A balance is said be sensitive if it can measure small change in mass.

**Other balance that we can be used to measure mass are:**

Direct balance, Dial balance and Lever balance.

In absence of the balance for mass measurement , we can roughly measure mass of object using a uniform meter rule balanced at center.

You suspend a known mass Mo 10cm from center O. then suspend an unknown Mass at the other side of meter rule , and adjust the position until rule is balanced again. Let x= the distance of M from the center o. then calculate the unknown mass using the principle of moment.

- Mo x 10cm =M * x
- M =10/x

#### Measurement of weight

Weight is measured using Spring balance, note that mass and weight cannot be measured with the same equipment, because mass is different from weight.

#### Difference between mass and weight

WEIGHT | MASS |

Weight is the force of gravity on a body | Mass is the quantity of matter a body contains |

It is a vector quantity | It is a scale quantity |

It has magnitude and direction | It has only magnitude |

The unit of measurement is NEWTON (N) | The unit of measurement is kilogram (kg) |

##### Measurement of volume

The volume of a liquid in cubic centimeter or millimeters can be measured using measuring cylinder, measuring flask, pipettes or burette

The volume of **irregular solid** can be obtained by putting completely the solid in a cylinder that contains liquid. The irregular solid will displace some liquid. The volume of the liquid displaced is equal to the volume of the irregular solid. But make sure that the solid those not dissolve it the liquid.

The volume of regular solid can be obtained by the following formulas:

Volume of a sphere = 3/4πr^{3}

Volume of a box = L x b x h

Volume of cone =3/4 (base area x height)

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