Question:
Which force is responsible for tides in the ocean at night ?
Answer:
It is the gravitational pull of Moon on sea water.
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.
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 4.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 5.
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 6.
Is weight a scalar quantity?
Q 7.
What is the value of ‘g’ at the centre of Earth ?
Q 8.
Why do sewing needles and all pins have a sharp pointed tip?
Q 9.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 10.
What do you mean by acceleration due to gravity ?
Q 11.
The distance between two objects is doubled. What happens to gravitational force between them
Q 12.
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 13.
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 14.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 15.
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 16.
What is the gravitational force between the Earth and a body called? In which direction does it occur?
Q 17.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 18.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 19.
Can a body have weight but no mass ?
Q 20.
Fill in the blanks :
Geocentric model i.e. the Earth is the orbital centre of all celestial bodies was proposed by _____.
Q 21.
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 22.
(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 23.
Name the scientist who identified the relation about force of gravitation. Name the law.
Q 24.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 25.
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Q 26.
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Q 27.
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 28.
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 29.
Then why Is the Earth not seen moving towards the stone ?
Q 30.
What are the Kepler Laws that govern the motion of the planets?
Q 31.
Who measured the value of G first time, experimentally?
Q 32.
Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?
Q 33.
Define weight? How it is related to mass?
Q 34.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 35.
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 36.
Fill in the blanks :
The SI unit of mass is ______.
Q 37.
The pressure at the bottom of a filled glass (density = 1000 kg/m
3) of water is P. The water is taken out and the glass is filled with kerosene oil (density = 817.5 kg/m
3). Now the pressure at the bottom will be a. same as P b. smaller than P c. larger than P d. cannot be determined.
Q 38.
What is the acceleration of free fall ?
Q 39.
Who gave three laws of planetary motion ?
Q 40.
Does Newton’s third law of motion apply to gravitational force ?
Q 41.
A body is just dropped from a height What is its initial velocity ?
Q 42.
What is the weight of a body of mass 1 kg on Earth ?
Q 43.
Can a body have mass but no weight ?
Q 44.
How are gravitation and gravity related ?
Q 45.
Write down the equations of motion of objects under the influence of gravitational force of Earth.Explain the meaning of the symbols used.
Q 46.
Define g and G.Establish relation between them.
Q 47.
On earth,value of G =
.What is its value on moon,where g is nearly
th that of earth ?
Q 48.
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 49.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 50.
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.
