1. The instrument used to measure atmospheric pressure is called Barometer.
2. It consists of a long glass tube which is closed at one end, open at the other filled with mercury and turned upside down in a container of mercury.
3. This is done by closing the open end of the mercury filled tube with the thumb and then opening it after immersing it in to a trough of mercury.
4. The Barometer works by balancing the mercury in the glass tube against the outer air pressure.
5. If the air pressure increases, it pushes more of the mercury up into the tub and if the air pressure decreases, more of the mercury drains from the tube.
6. The space between mercury and closed end is vacuum, since vacuum cannot exert any pressure, the level of mercury in the tube provides a precise measure of air pressure, which is called atmospheric pressure.
7. This type of instrument can be used in a lab or weather station.

Meristematic tissues are group of immature cells that are capable of undergoing cell division. They occur in zones where grown can take place in plants.
Types of Meristems:

Plaster of paris should be stored in a moisture-proof container as it absorbs water from moisture present in air and turn into hard substance (Gypsum).

In a household electric circuit, different home appliances are connected in parallel to one another due to the following reasons:
(i) The appliances can be operated independently. If one appliance is switched off, others remain unaffected.
(ii) Each appliance gets the same constant voltage.
(iii) In parallel connection of electrical appliances, the overall resistance of the circuit is reduced due to which the current from the power supply is high.

Hot air balloons:
Air molecules at the bottom of the balloon get heated by a heat source and rise. As the warm air rises, cold air is pushed downward and it is also heated. When the hot air is trapped inside the balloon, it rises.
Breezes:
During day time, the air in contact with the land becomes hot and rises. Now the cool air over the surface of the sea replaces it. It is called sea breeze. During night time, air above the sea is warmer. As the warmer air over the surface of the sea rises, cooler air above the land moves towards the sea. It is called land breeze.
Winds:
Air flows from area of high pressure to area of low pressure. The warm air molecules over hot surface rise and create low pressure. So, cooler air with high pressure flows towards low pressure area. This causes wind flow.
Chimneys:
Tall chimneys are kept in kitchen and industrial furnaces. As the hot gases and smoke are lighter, they rise up in the atmosphere.

Vitamins are vital nutrients, required in minute amounts to perform special functions to maintain a healthy body. It is deficiency in the food it cause many diseases.

Data processing has six steps. They are:
Data collection
Data storage
Data sorting
The data processing
Data analysis
Data presentation and conclusions

(i) Atom has a very small nucleus at the centre.
(ii) There is large empty space around the nucleus.
(iii) Entire mass of an atom is concentrated in a very small positively charged region which is called the nucleus.
(iv) Electrons are distributed in the vacant space around the nucleus.
(v) The electrons move in circular paths around the nucleus.
 

Speed of the train = 90 kmph
Speed of the train = \(\frac { 90000 }{ 3600 } \)
Speed of the train =\(\frac { 900 }{ 36 } \)=25
Speed of the train = 25 m/s.
V = 25 m/s
a = - 0.5 ms^-2
Displacement = \(\frac { V }{ a } =\frac { 25 }{ 0.5 } =\frac { 25 }{ -0.5 } \) = 50 seconds
S = ut + \(\frac { 1 }{ 2 } \)at²
= 25 x 50 - \(\frac { 1 }{ 2 } \) x 0.5 x 50² = 1250 - 625
Distance covered by the train before it is brought to rest = 625 m/s.

\(\frac { 1 }{ f } =\frac { 1 }{ u } +\frac { 1 }{ v } \)
\(\frac { 1 }{ 20 } =\frac { 1 }{ -600 } +\frac { 1 }{ v } \)
\(\frac { 1 }{ v } =\frac { 1 }{ 20 } -\frac { 1 }{ -600 } \)
= \(\frac { 1 }{ 20 } +\frac { 1 }{ 600 } \)
\(\frac { 1 }{ v } =\frac { 30+1 }{ 600 } =\frac { 31 }{ 600 } \)
\(v=\frac { 600 }{ 31 } \)
= 19.35 cm
b) Size of the image
\(m=\frac { -v }{ u } \)
= \(-\frac { v }{ (-u) } =\frac { -600 }{ 31 } \times \frac { 1 }{ -600 } \)
m=\(\frac { 1 }{ 31 } \)
Breadth of image =\(\frac { 1 }{ 31 } \)\(\times\)200 cm= 6.45 cm
Height of image = \(\frac { 1 }{ 31 } \) \(\times\)160 cm= 5.16 cm

The thickness of coin (one rupee) is finding with the help of screw gauge:
1. Determine the pitch, least count and the zero error of the screw gauge.
2. Place the coin between two studs.
3. Rotate the head until the coin is held firmly but no tightly with the help of the ratchat.
4. Note the reading of a pitch scale crossed by the head scale and the head scale (PSR) division that coincides with the pitch scale axis (HSC).
5. The thickness of the coin is given by PSR + (HSR + ZC) x LC. Repeat the experiment for the different position of the coin.
6. Tabulate the reading.
7. The average of the reading given the thickness of the coin.

The thickness of one rupee coin is = 1.33 mm.

Brownian movement:
When colloidal solution are viewed under powerful microscope, it can be seen that colloidal particles are moving constantly and rapidly in zig-zag directions. The Brownian movement of colloidal particles is due to the unbalanced bombardment of the particles by the molecules of dispersion medium.
Example: Motion of pollen grains in water.

Tyndall effect: 
Tyndall (1869) observed that when a strong beam of light is focused on a colloidal solution the path of the beam becomes visible. This phenomenon is known as Tyndall effect and the illuminated path is called Tyndall cone. This phenomenon is not observed in case of true solution.
Example: When fine beam of light pass through the true solution, the light is invisible but the enters the colloidal solution the light is visible.