Subject :NSO Class : Class 6
Ans 1:
Class : Class 10
Wet' is ultimately just a word that applies to water. What we feel as wetness is actually coldness as the water evaporates. Below is an experiment from the Institute of Physics to test the feeling of 'wetness' between two different liquids: "The feeling of wetness is actually coldness. You can test this by comparing water with another liquid - cooking oil - which doesn't evaporate so freely. Fill two small cups (egg-cups are ideal) - one with water, and the other with cooking oil. (Young children should ask an adult to help.) Let both liquids come to room temperature for a day, or overnight. Dip one index finger in each liquid, lift them out, and then observe for a few minutes." Explanation: Liquids make surfaces wet (i.e. they stick to many solid surfaces) due to the electrostatic (opposite charges) forces between molecules. Water is polar—it has an uneven spread of electrical charge—which makes one end of the molecule positive and the other end negative. This causes water to be attracted to many surfaces and also explains many other properties of water.
Ans 3:
Class : Class 9
Wet' is ultimately just a word that applies to water. What we feel as wetness is actually coldness as the water evaporates. Below is an experiment from the Institute of Physics to test the feeling of 'wetness' between two different liquids: "The feeling of wetness is actually coldness. You can test this by comparing water with another liquid - cooking oil - which doesn't evaporate so freely. Fill two small cups (egg-cups are ideal) - one with water, and the other with cooking oil. (Young children should ask an adult to help.) Let both liquids come to room temperature for a day, or overnight. Dip one index finger in each liquid, lift them out, and then observe for a few minutes." Explanation: Liquids make surfaces wet (i.e. they stick to many solid surfaces) due to the electrostatic (opposite charges) forces between molecules. Water is polar—it has an uneven spread of electrical charge—which makes one end of the molecule positive and the other end negative. This causes water to be attracted to many surfaces and also explains many other properties of water.
Ans 4:
Class : Class 4
Wet' is ultimately just a word that applies to water. What we feel as wetness is actually coldness as the water evaporates. Below is an experiment from the Institute of Physics to test the feeling of 'wetness' between two different liquids:
"The feeling of wetness is actually coldness. You can test this by comparing water with another liquid - cooking oil - which doesn't evaporate so freely. Fill two small cups (egg-cups are ideal) - one with water, and the other with cooking oil. (Young children should ask an adult to help.) Let both liquids come to room temperature for a day, or overnight. Dip one index finger in each liquid, lift them out, and then observe for a few minutes."
Explanation: Liquids make surfaces wet (i.e. they stick to many solid surfaces) due to the electrostatic (opposite charges) forces between molecules. Water is polar—it has an uneven spread of electrical charge—which makes one end of the molecule positive and the other end negative. This causes water to be attracted to many surfaces and also explains many other properties of water.
Study the flow chart carefully.
A mass of 100 g strikes the wall with speed 5 m/s at an angle as
shown in figure and it rebounds with the same speed. If the contact time is 2 x 10-3 sec, what is the force applied by the wall ?
to right 
to left 
