Chapter 1: Measurements and Units

**Physical Quantity**is a quantity that can be measured. It consists of a numerical magnitude and a unit.

Numbers written using powers of ten are in

**scientific notation**or**standard form.**For example;

Are set systematic international units, for measuring mass, time, and other base units and derived quantities.

Is the measure of the amount of substance in an object.

Has the following effects:

all objects are attracted to the Earth. The greater the mass of an object, the stronger is he Earth’s gravitational pull on it.

all objects resist attempts to make them go faster, slower, or in a different direction. The greater the mass, the greater is the resistance to change in motion.

SI base unit is

__kilogram (kg).__

SI base unit is

__second (s).__Following are some of other units for second:

SI base unit is

__metre (m).__

**Ruler**can be used to measure small distances of a few centimetres (cm).They are able to measure to the nearest millimetre (mm).

Can measure upto one metre.

Example of usage:

height of the table

**Micrometer**is used to measure objects that are too small to be measured with__vernier calipers__Gives a precision of 0.01 mm

Can measure measurements of less than 25 cm.

Example of usage:

diameter of a wire

**Vernier Calliper**is a useful tool for measuring both internal and external diameters.They are able to measure to a precision of 0.01 cm.

Time intervals of many

__seconds__or__minutes__can be measured using a a**stopwatch.**Some instruments have analogue or a digital display.

It is the quantity of space an object takes up.

It’s SI unit is

__cubic metre (m^3).__

It is the quantity of mass per unit volume of a substance.

__Formula:__Density= Mass/Volume

ρ=m/v

ρ is a greek letter ‘rho’ .

(both equations are same, written in different ways; i.e first one is the word equation and the other one is symbolic equation.

SI unit of density is

__kilogram per cubic metre (kg m^-3).__Objects that are less dense than water will float on water; and objects that are denser than water will sink.

Its volume can be measured using a measuring cylinder.

Most cylinders have scale marked in

__millilitres (ml)__or__cubic centimetres (cm^3).__

If an object has a simple shape, its volume can be calculated through formula. For example:

volume of a regular block = length x width x height

If the shape of the object is too awkward to calculate its volume, then immerse the object in a measuring cylinder filled with water and then calculate the increase in water level. This value will be the volume of the object.

Once volume of the object is obtained through one of the above methods suitable, find the mass of the object using a balance.

Following is one of the example:

An easy method of finding the density of a liquid is by using a small float called

**hydrometer**.

The relative density on a hydrometer indicates the

*relative density*of the liquid.Checks like these are important in some production processes.

**Physical Quantity**is a quantity that can be measured. It consists of a numerical magnitude and a unit.

Numbers written using powers of ten are in

**scientific notation**or**standard form.**For example;

Are set systematic international units, for measuring mass, time, and other base units and derived quantities.

Is the measure of the amount of substance in an object.

Has the following effects:

all objects are attracted to the Earth. The greater the mass of an object, the stronger is he Earth’s gravitational pull on it.

all objects resist attempts to make them go faster, slower, or in a different direction. The greater the mass, the greater is the resistance to change in motion.

SI base unit is

__kilogram (kg).__

SI base unit is

__second (s).__Following are some of other units for second:

SI base unit is

__metre (m).__

**Ruler**can be used to measure small distances of a few centimetres (cm).They are able to measure to the nearest millimetre (mm).

Can measure upto one metre.

Example of usage:

height of the table

**Micrometer**is used to measure objects that are too small to be measured with__vernier calipers__Gives a precision of 0.01 mm

Can measure measurements of less than 25 cm.

Example of usage:

diameter of a wire

**Vernier Calliper**is a useful tool for measuring both internal and external diameters.They are able to measure to a precision of 0.01 cm.

Time intervals of many

__seconds__or__minutes__can be measured using a a**stopwatch.**Some instruments have analogue or a digital display.

It is the quantity of space an object takes up.

It’s SI unit is

__cubic metre (m^3).__

It is the quantity of mass per unit volume of a substance.

__Formula:__Density= Mass/Volume

ρ=m/v

ρ is a greek letter ‘rho’ .

(both equations are same, written in different ways; i.e first one is the word equation and the other one is symbolic equation.

SI unit of density is

__kilogram per cubic metre (kg m^-3).__Objects that are less dense than water will float on water; and objects that are denser than water will sink.

Its volume can be measured using a measuring cylinder.

Most cylinders have scale marked in

__millilitres (ml)__or__cubic centimetres (cm^3).__

If an object has a simple shape, its volume can be calculated through formula. For example:

volume of a regular block = length x width x height

If the shape of the object is too awkward to calculate its volume, then immerse the object in a measuring cylinder filled with water and then calculate the increase in water level. This value will be the volume of the object.

Once volume of the object is obtained through one of the above methods suitable, find the mass of the object using a balance.

Following is one of the example:

An easy method of finding the density of a liquid is by using a small float called

**hydrometer**.

The relative density on a hydrometer indicates the

*relative density*of the liquid.Checks like these are important in some production processes.