IMPORTANTIMPORTANT NOTES NOTES IMPORTANT NOTES
7. Acceleration due to gravity of the Earth : The acceleration with which the bodies fall towards the earth is called acceleration due to gravity. Its average value is 9.81 ms–2. 8. Variation of acceleration due to gravity. (i) Acceleration due to gravity changes with the change in distance from the centre of the earth. (ii) Acceleration due to gravity is maximum at the poles of the earth. Its value decreases as we move towards the equator, such that its magnitude is least at the equator. (iii) Acceleration due to gravity decreases as we move inside the earth, such as deep mines. (iv) Acceleration due to gravity decreases as we move away from the surface of the earth, such as on the mountains, in aeroplanes, in spaceships, etc. 9. Mass : The amount of matter contained in a body is called mass. It is a scalar quantity and is measured by a physical balance. It is always a constant quantity and its unit in SI system is kilogram. 10. Weight : The force with which a body is attracted towards the centre of the Earth is called weight.
I. VERY SHORT ANSWER QuESTIONS
Assignments for summAtive Assessment
7. Why are sleepers used below the rails? [2010 (T-I)] 8. The gravitational force between two objects is F. How will the force change when the distance between them is reduced to 1/4 th? [2010 (T-I)] 9. What is meant by buoyant force? [2010 (T-I)] 10. A body of weight 20 N floats half submerged in a liquid. What is the buoyant force on the body? [2010 (T-I)] 1
1. State a relation between thrust and pressure. [2010 (T-I)] 2. State any one phenomena related to the Universal Law of Gravitation. [2010 (T-I)] 3. State Archimedes principle. [2010 (T-I)] 4. State universal law of gravitation. [2010 (T-I)] 5. State two factors in which the gravitational force between two objects depends. [2010 (T-I)] 6. What is the gravitational force...