1. A force of 100N is applied to an object of area 2m2.Calculate the pressure.
Here, force = 100 N
And, area = 2 m2
Now, putting these values in the formula
Pressure = Force/Area
= 100 N/2 m2
= 50 N/m2 (or 50 Pa)
2. A sharp knife cuts better than a blunt knife.Give reason.
A sharp knife has a very thin edge to its blade. A sharp knife cuts objects (like vegetables) better because due to its very thin edge, the force of our hand falls over a very small area of the object producing a large pressure. And this large pressure cuts the object easily. On the other hand, a blunt knife has a thicker edge. A blunt knife does not cut an object easily because due to its thicker edge, the force of our hand falls over a larger area of the object and produces lesser pressure. This lesser pressure cuts the object with difficulty.
3. Water tanks are built on top of hills or on tall pillars. Why?
Water stored at a higher level exerts greater pressure downwards. So water flows through pipes in sufficient pressure to reach even at tall buildings.
4. At high altitudes mountaineers some times have nasal bleeding. Explain why this happens?
Atmospheric pressure decreases with height. Whenever the mountaineers go upwards the atmospheric pressure becomes less than that of the pressure inside the body and hence the minute blood vessels break due to high pressure and have the possibility of nasal bleeding. In order to prevent this use clothes filled with air having atmospheric pressure.
5. An empty metal vessel floats on water but it sinks when filled with water.
An empty metal vessel displaces water equal to its weight and floats initially. But as more water enters the vessel it sinks more displacing more water. When more and more water enters the vessel and it reaches a stage when it cannot displace any more water it sinks.
6. Define buoyant force. What is the basis for buoyant force?
The force exerted upwards by a liquid when a body is completely or partially immersed in it is called buoyant force. The difference in the liquid pressure, felt on the top and bottom surface of an object, immersed in a liquid is the basis for buoyant force.
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