Worksheet solutions for chapter: Gravitation for class 9 are provided below.
(2) Find the pressure exerted by 10 boxes of 20 kg of mass each. The length of the box is 2 m and breadth of 1 m.
(4) What is Archimedes principle and write importance of the principle.
Ans- The Archimedes’ Principle is stated as follows-
When a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.
Eg:- Tie a stone at the end of the rubber string. Suspend the stone by holding the other end. Note the elongation of the string. Dip the string in the water. Now note the elongation of the string. It will decreases as the stone is gradually lowered in water. It means that the upward force (Buoyant force) is acting on the stone. As a result, the net force on the stone decreases and hence, the elongation also decreases.
Applications of the Archimedes’ principles-
(i) It is used in designing ships and submarines.
(ii) Lactometers which are used to determine the purity of a sample of milk and hydrometers used for determining density of liquids.
(6) Write “T” if statement is true and write “F” if statement is false.
(i) The accepted value of G is 6.673 10-11 Nm2kg-2.
(ii) The value of g at poles smaller at the poles than at the equator.
(iii) The weight of the object remains same everywhere.
(iv) The upward force exerted by the water or fluid on the object is known as upthrust or buoyant force.
(i) The accepted value of G is 6.673 10-11 Nm2kg-2.”T”
(ii) The value of g at poles smaller at the poles than at the equator. “F”
(iii) The weight of the object remains same everywhere. “F”
(iv) The upward force exerted by the water or fluid on the object is known as upthrust or buoyant force. “T”
(8) The volume of a block is 400 m3. Will the packet float or sink in water if the density of water is 1 kg m-3? What will be the mass of the water displaced by this packet?
(10) There are three jar with water. In one jar the object sinks and in another jar second object floats on the water. Which object has higher density than the water?
Ans- If density of the object is greater than the density of the water, the object will sink. Therefore, the object of jar (a) has greater density than the density of the water.
If density of the object is lower than the density of the water, the object will float. Therefore, the object of jar (b) has lower density than the density of the water.