Question:
Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 1024 kg and of the Sun = 2 × 1030 kg. The average distance between the two is 1.5 × 1011 m.
Answer:
Given, mass of the earth (mE) = 6 × 1024 kg
mass of the sun (mS) = 2 × 1030 kg
Distance between the bodies (d) = 1.5 × 1011m
Gravitational Constant (G) = 6.67 × 10-11 Nm2/kg2
Applying formula of Newton's Law of Gravitation,
F = GmEmS/d2 = 6.67 × 10-11 × 6 × 1024 × 2 × 1030 / (1.5 × 1011)2
F = 80.04 × 10-11+24+30/ 2.25 × 1022 = 35.57 × 1043-22 = 35.57 × 1021
F = 3.56 × 1022N
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
What do we call the gravitational force between the Earth and an object ?
Q 3.
In Fig.,the line that joins a planet to the sun sweeps out areas
,
in time intervals 6 weeks,3 weeks and 2 weeks respectively.How are
,
realted ?
Q 4.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 5.
Is weight a scalar quantity?
Q 6.
The weight of an empty glass is 1 N. When completely filled with water, the glass weighs 4 N. If you now throw the water away and fill the glass partly with sand, the weight becomes 4 N. If the rest of the glass is now filled up with water, the weight becomes 6 N. What is the relative density of sand?
Q 7.
The distance between two objects is doubled. What happens to gravitational force between them
Q 8.
Calculate the force of gravitation between the Earth and the Sun,given that the mass of the Earth =
kg and mass of the Sun =
kg. The average distance between the two is
m.
Q 9.
State Kepler’s Laws of planetary motion.
Q 10.
A physics teacher explains to his students in class,the subject of motion under gravity.When a body is projected upwards from the ground with a certain velocity a,the velocity goes on decreasing at a constant rate due to gravitational pull of earth.At a certain height,this velocity becomes zero.The body cannot rise further.From this maximum height,the body begins to fall and its velocity goes on increasing at the same constant rate due to gravitational pull of earth.The body would strike the ground with exactly the same velocity (v = u),with which it was thrown initially. This is on the assumption that resistance due to air is zero, either way.
Read the above passage and answer the following questions:
(i) Why is velocity of body on striking the ground the same as initial velocity of projection of the body ?
(ii) Does the body take same time to fail to ground as the time it takes to reach the maximum height ?
(iii) What values of life do you learn from this brief study ?
Q 11.
At what height above the surface of the earth, the value of 'g' becomes 64% of its value at the surface of the earth. Take radius of the earth = 6400 km.
Q 12.
Two bodies A and B having masses 2 kg and 4 kg respectively are separated by 2 m.Where should a body of mass 1 kg be placed so that the gravitational force on this body due to bodies A and B is zero ?
Q 13.
What do you mean by acceleration due to gravity ?
Q 14.
Why will a sheet of paper fall slower than one that is crumpled into a ball ?
Q 15.
What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?
Q 16.
What is the value of ‘g’ at the centre of Earth ?
Q 17.
A body is just dropped from a height What is its initial velocity ?
Q 18.
What is the SI unit of weight ?
Q 19.
Two particles of equal mass (m) move in a circle of radius (r) under the action of their mutual gravitational attraction. Find the speed of each particle.
Q 20.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 21.
(a) What is the relationship between g and G?
(b) Show mathematically whether g (acceleration due to gravity on the earth) depends on the mass of the object itself or not.
(c) Show that for a given location on the surface of the earth g is almost constant.
Q 22.
Define weight? How it is related to mass?
Q 24.
Fill in the blanks :
The acceleration which causes changes only in direction of the velocity of a body is called __________ and it is always directed ___________ the circle.
Q 25.
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Q 26.
State the universal law of gravitation.
Q 27.
A stone is thrown vertically upward with an initial velocity of 40 m/s.Taking g =
,find the maximum height reached by the stone.What is the net displacement and the total distance covered by the stone ?
Q 28.
Then why Is the Earth not seen moving towards the stone ?
Q 29.
Does value of ‘g’ vary from place to place on Earth ?
Q 30.
Can a body have mass but no weight ?
Q 31.
Fill in the blanks :
The mass of an object _____ (varies/does not vary) on the earth as well as on the moon. But its weight is ______(same/different) on both places.
Q 32.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 33.
Fill in the blanks :
The SI unit of weight is _____.
Q 34.
Who measured the value of G first time, experimentally?
Q 35.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 36.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 37.
Write the standard equations in the form when an object is dropped from a height?
Q 38.
A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate(i) the maximum height to which it rises.(ii)the total time it takes to return to the surface of the earth.
Q 39.
Is mass a scalar quantity?
Q 40.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
Q 41.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 42.
Fill in the blanks :
A body is said to be in _______ when only gravity acts on it.
Q 43.
Fill in the blanks :
The SI unit of mass is ______.
Q 44.
Fill in the blanks :
All other variables remaining constant, the force of gravitation is ________ proportional to the square of distance between the two objects.
Q 45.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 46.
What do you mean by Thrust or Buoyant force?
Q 47.
Why does an object float or sink when placed on the surface of the water?
Q 48.
In what direction does the buoyant force on an object immersed in a liquid act?
Q 49.
The volume of a 500 g sealed packet is 350 cm
3. Will the packet float or sink in water if the density of water is 1 g cm
-3? What will be the mass of the water displaced by this packet?
Q 50.
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
