Ans. Air exerts pressure on the inner walls of balloon causes it to expand and get inflated.
Ans. The wide belts increase the area and reduce the pressure. This avoids sinking of the tank into the ground.
Ans. The force acting on a unit area of a surface is called pressure.
Pressure = force / area on which it acts
Ans. It is the force of friction between the surface of the ball and the ground that brings the moving ball to rest.
Ans. The force resulting due to the action of muscles is known as the muscular force. Example: lifting a bucket of water.
Ans. A change in either the speed of an object, or its direction of motion, or both, is described as a change in its state of motion.
Ans. Force that can be applied only when it is in contact with an object, it is also called a contact force. Example: lifting a bucket of water.
Ans. A magnet can exert a force on another magnet without being in contact with it. The force exerted by a magnet is an example of a non-contact force.
Ans. The high pressure produced by the gas or water molecules on the walls of balloon causes it to expand and get inflated.
Ans. This is so because water pressure is less in the upstairs tap due to lesser depth.
Ans. We do not get crushed because the atmospheric pressure acting on our body from outside is balanced by the blood pressure acting from inside.
Ans. The force that always acts on all the moving object and its direction is always opposite to the direction of motion is called frictional force (or friction).
Ans. Lesser the area, larger the pressure for the same force applied. Therefore it is easier to cut with sharp knives than blunt ones, with same force.
Ans. The atmospheric air extends up to many kilometres above the surface of the earth. The pressure exerted by this air is known as atmospheric pressure.
Ans. The examples of contact forces are:
i. Muscular force
ii. Frictional force
Ans. When a blacksmith hammers a hot piece of iron, he uses his muscular force. This muscular force changes the shape of the iron.
Ans. A force that can be exerted by an object even from a distance is called a non-contact force. The force exerted by a magnet is an example of a non-contact force.
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