Ch 6 Physics Class 11 Notes

• Very Important Multiple Choice Questions (MCQs) with Answers of the Gravitation Ch 6 Physics Class 11 Notes in Physics Class 11 Sindh Book Boards.
• State and explain Newton's law of gravitation
• Explain mass of Earth
• Variation of G with altitude
• Variation of G with Depth
• Define and explain about Weightlessness with (i) When Elevator is at Rest (ii) When Elevator is Ascending with an Acceleration 'a' (iii) When Elevator is Descending with Acceleration 'a' (iv) When the Elevator is falling freely Under the Action of Gravity
• Introduction to Artificial Gravity and explain it.
• A 10 kg mass is at a distance of 1 m from a 100 kg mass. Find the gravitational force of attraction when (i) 10 kg mass exerts force on the 100 kg mass (ii) 100 kg mass exerts force on the 10 kg mass.
• Compute gravitational acceleration at the surface of the planet Jupiter which has a diameter as 11 times as compared with that of the earth and a mass equal to 318 times that of earth. 
• The mass of the planet Jupiter 1.9 x 1027 kg and that of the sun is 2.0 x 1030 kg. If the average distance between them is 7.8 x 1011 m, find the gravitational force of the sun on Jupiter. 
• The radius of the moon is 27% of the earth’s radius and its mass is 1.2% of the earth’s mass. Find the acceleration due to gravity on the surface of the moon. How much will a 424N body weight there? 
• What is the value of the gravitational acceleration at a distance of (i) earth’s radius above the earth’s surface? (ii) Twice earth’s radius above the earth’s surface? 
• At what distance from the center of the earth does the gravitational acceleration have one half the value that it has on the earth’s surface?
• Compute the gravitational attraction between two college students of mass 80 & 50 kg respectively, 2m apart from each other. Is this force worth worrying about?
• Determine the gravitation between the proton and the electron in a hydrogen atom, assuming that the electron describes a circular orbit with a radius of 0.53x10-10 m (mass of proton = 1.67x10-27 kg, mass of electron = 9.1x10-31 kg).
• A woman with a mass of 45 kg is standing on a scale in an elevator. The elevator accelerates with a constant acceleration of 1.2 m/s2 . What is the women’s weight as measured by her in the elevator. 
• At what height from center of the earth, the value of g becomes 36% of its value on the surface of earth?
• Calculate the centripetal force acting on a man whose mass is 64kg when resting on the ground at the equator. (Radius of the earth = 6.4 x106 m.)
• How many times in a second does a spaceship of diameter 30 m, needed to be rotated in order to create artificial gravity? 
• A man weighing 60 kg is standing on the floor of an elevator. Calculate the force exerted by the man when the elevator is ascending at a rate of 2 m/s2.
• The ratio of acceleration due to gravity inside a deep mine to that on the surface of earth is 0.99.Find the depth of the mine, assuming that the density of earth is uniform. Take the radius of earth as 𝟔.𝟑𝟖 × 𝟏𝟎 𝟔𝒎.
• At what distance from centre of earth does the gravitational acceleration have one third of the value that it has on the earth's surface?
• The mass of the moon is approximately one eightieth (1/80) of the earth's mass and its radius is one fourth (1/4) that of earth. Find the acceleration due to gravity on the surface of the moon.