Question:
State Kepler’s Laws of planetary motion.
Answer:
Refer to Art 3.8,Pages 146 to 147.
Gravitation
Q 1.
State the universal law of gravitation.
Q 2.
Fill in the blanks :
A body is said to be in _______ when only gravity acts on it.
Q 3.
What is the SI unit of weight ?
Q 4.
Comment on application of Newton’s third law of motion to gravitation.Illustrate by examples.
Q 5.
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 6.
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 7.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 8.
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 9.
What is the value of ‘g’ at the centre of Earth ?
Q 10.
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 11.
Is mass a scalar quantity?
Q 12.
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 13.
As you climb up a mountain, your ears “pop” because of the changes in atmospheric pressure. In which direction, outward or inward, does your eardrum move when you climb up?
Q 14.
An object is thrown vertically upwards and rises to a height of 10 m. Calculate (i) the velocity with which the object was thrown upwards and (ii) the time taken by the object to reach the highest point.
Q 15.
What is the relation between g and G ?
Q 16.
Fill in the blanks :
Geocentric model i.e. the Earth is the orbital centre of all celestial bodies was proposed by _____.
Q 17.
Fill in the blanks :
The SI unit of weight is _____.
Q 18.
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 19.
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 20.
What is the value of G (i) on Earth (ii) on Moon ?
Q 21.
Which force revolves Moon around Earth ?
Q 22.
The distance between two objects is doubled. What happens to gravitational force between them
Q 23.
Which force accelerates a body in free fall ?
Q 24.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
Q 25.
Where is ‘g' maximum, on the surface of Earth, above the surface or below the surface of Earth ?
Q 26.
What is the SI unit of mass ?
Q 27.
Can a body have mass but no weight ?
Q 28.
How are gravitation and gravity related ?
Q 29.
Can you calculate mass of Earth from Newton’s law of gravitation ?
Q 30.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 31.
How gravitational force is different from or similar to magnetic force (between two magnets) or coulomb force (between two charged object)?
Q 33.
Write the standard equations in the form when an object is dropped from a height?
Q 34.
A ball is thrown with some velocity 'u' m/s. Show that under free fall, it will fall the ground with same velocity.
Q 35.
When a ball is thrown upwards, it falls back to the ground. Name the force which makes it fall.
Q 36.
Name the scientist who identified the relation about force of gravitation. Name the law.
Q 37.
Fill in the blanks :
Motion of body with constant speed in a circular path is called ______________.
Q 38.
Fill in the blanks :
It is the ____________ of the earth, which holds our atmosphere in place.
Q 40.
The volume of 50 g of a substance is 20 cm
3. If the density of water is 1 g cm
-3, will the substance float or sink?
Q 41.
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Q 42.
Why do sewing needles and all pins have a sharp pointed tip?
Q 43.
The volume of 50g of a substance is 20 cm
3. If the density of water is 1g/cm
3, will the substance float or sink?
Q 44.
If the distance of Earth from the Sun were half the present value,how many days will make one year ?
Q 45.
Distinguish between gravitation and gravity.
Q 46.
Compare gravitational force between light objects and heavy objects.
Q 47.
What is the importance of Universal Law of Gravitation?
OR
Q: State any one phenomena related to the Universal Law of Gravitation.
Q 48.
How is gravitational force of attraction between two bodies affected if(i) Mass of both bodies is doubled.(ii) Distance between them is halved.
Q 49.
(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 50.
In what direction does the buoyant force on an object immersed in a liquid act?
