Question:
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.
Answer:
The two particles will move on a circular path if they always remain diametrically opposite as shown in Fig. , so that gravitational force on one particle due to the other is directed along the radius. This would provide the necessary centripetal force i.e.,
F== or v=
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
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 3.
What do we call the gravitational force between the Earth and an object ?
Q 4.
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 5.
Why do sewing needles and all pins have a sharp pointed tip?
Q 6.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 7.
Is weight a scalar quantity?
Q 8.
What do you mean by acceleration due to gravity ?
Q 9.
What is the value of ‘g’ at the centre of Earth ?
Q 10.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
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.
Suppose a planet exists whose mass and radius both,are half those of Earth.Calculate the acceleration due to gravity on the surface of this planet.
Q 13.
What is the gravitational force between the Earth and a body called? In which direction does it occur?
Q 14.
Two stones A and B are dropped from a multistoried building. A is dropped from 100 m and after some time B is dropped from 50 m height. Both of them reach the earth at the same time. Will they have equal velocity while reaching the ground ? Calculate and find out the answer (take g =10 m/s
2).
Q 15.
The distance between two objects is doubled. What happens to gravitational force between them
Q 16.
Can a body have weight but no mass ?
Q 17.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 18.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 19.
A particle is dropped from a tower 180 m high.How long does it take to reach the ground ? What is the velocity when it touches the ground ? Take g =
Q 20.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 21.
Who gave three laws of planetary motion ?
Q 22.
What is the weight of a body of mass 1 kg on Earth ?
Q 23.
Fill in the blanks :
Geocentric model i.e. the Earth is the orbital centre of all celestial bodies was proposed by _____.
Q 24.
Who measured the value of G first time, experimentally?
Q 25.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 26.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 27.
Fill in the blanks :
The SI unit of mass is ______.
Q 28.
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 29.
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Q 30.
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Q 31.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 32.
A ball is thrown up with a speed of 15 m/s.How high will it go before it begins to fall ? Take g=
Q 33.
Does Newton’s third law of motion apply to gravitational force ?
Q 34.
How are gravitation and gravity related ?
Q 35.
Define g and G.Establish relation between them.
Q 36.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 37.
Fill in the blanks :
The force of attraction between two objects is ______ proportional to the product of their masses and _____ proportional to the square of a distance between them.
Q 38.
Fill in the blanks :
Acceleration due to gravity (g) is _______ (dependent/independent) of mass.
Q 39.
Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 10
24 kg and of the Sun = 2 × 10
30 kg. The average distance between the two is 1.5 × 10
11 m.
Q 40.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 41.
(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 42.
Define weight? How it is related to mass?
Q 43.
Name the scientist who identified the relation about force of gravitation. Name the law.
Q 44.
Fill in the blanks :
A body is said to be in _______ when only gravity acts on it.
Q 45.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 46.
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 47.
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 48.
If the distance between two masses is increased by a factor of 4,by what factor would the mass of one of them have to be altered to maintain the same gravitational force ?
Q 49.
A boy on a clif£ 49 m high drops a stone.One second later,he throws a second stone after the first.They both hit the ground at the same time. With what speed did he throw the second stone ?
Q 50.
State the universal law of gravitation.
