Question:
What was heliocentric theory? Who proposed this?
Answer:
Copernicus proposed heliocentric model around 1543 AD. he proposed that the sun is in the center and all planets move around it.
Gravitation
Q 1.
What is the SI unit of weight ?
Q 2.
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 3.
What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?
Q 4.
What is the SI unit of mass ?
Q 5.
Why don’t two objects move towards each other due to gravitational pull between them ?
Q 6.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go upwards from the earth's surface.
Q 7.
The following figure shows four containers containing a liquid at the same height. Rank them according to the pressure exerted by the liquid on the bottom of the containers in ascending order.
a. 1, 2, 3, 4 b. 4. 3, 1, 2 c. 3, 4, 1, 2 d. same pressure in each case.
Q 8.
What do you mean by free fall ?
Q 9.
What are the differences between the mass of an object and its weight ?
Q 10.
What is the value of G (i) on Earth (ii) on Moon ?
Q 11.
Does gravitational force between two objects depend on medium between them ?
Q 12.
What is the usual shape of orbits of planets around the Sun ?
Q 13.
How are gravitation and gravity related ?
Q 14.
Can you calculate mass of Earth from Newton’s law of gravitation ?
Q 15.
State Kepler’s Laws of planetary motion.
Q 16.
Write down the equations of motion of objects under the influence of gravitational force of Earth.Explain the meaning of the symbols used.
Q 17.
Fill in the blanks :
The value of G was found out by _______ by using a ________.
Q 18.
The mass of Sun is
kg and mass of Earth is
kg. If the distance between the centres of Sun and Earth is
km,calculate the force of gravitation between them.
Q 19.
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 20.
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 21.
Which force accelerates a body in free fall ?
Q 22.
Does Newton’s third law of motion apply to gravitational force ?
Q 23.
Then why Is the Earth not seen moving towards the stone ?
Q 24.
What is value of ‘g’ on Earth ?
Q 25.
Can a body have weight but no mass ?
Q 26.
A body weighs 10 kg on the surface of earth.What would be its mass and weight at the centre of earth ?
Q 27.
State and explain universal law of gravitation.What is its importance ?
Q 28.
Define g and G.Establish relation between them.
Q 29.
Whenever a body is thrown up with a certain velocity,the upward motion is opposed by gravitational pull of earth and also by the resistance of air.
Therefore, velocity of the body goes on decreasing. When this velocity becomes zero,the body cannot rise further.It has attained,what is called ‘maximum height’.From this height,the body begins to fall downwards under the action of gravity.
Read the above passage and answer the following questions:
(i) At the highest point,what are the velocity and acceleration of the body?
(ii) What is the maximum height attained by a body thrown upwards with a velocity of 19.6 m/s ? Take g =
.
(iii) What values in life do you learn from this concept ?
Q 30.
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 31.
Why is G called the Universal Constant?
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.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
Q 35.
If the distance of Earth from the Sun were half the present value,how many days will make one year ?
Q 36.
To estimate the height of a bridge over a river,a stone is dropped freely on the river from the bridge.The stone takes 2 s to touch the water surface in the river.Calculate the height of the bridge from the water level.Take g = 9.8
.
Q 37.
Write the formula to find the magnitude of the gravitational force between the Earth and an object on the surface of the Earth.
Q 38.
How does the force of gravitation between two objects change when the distance between them is reduced to half ?
Q 39.
What is the acceleration of free fall ?
Q 40.
What is the weight of a body of mass 1 kg on Earth ?
Q 41.
Distinguish between mass and weight.
Q 42.
The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with whichthe moon attracts the earth? Why?
Q 43.
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 44.
Fill in the blanks :
The SI unit of weight is _______.
Q 45.
The gravitational force between two objects is 100 N. How should the distance between these objects be changed so that force between them becomes 50 N ?
Q 46.
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 47.
A stone drops from the edge of the roof.It passes a window 2 m high in 0.1 s.How far is the roof above the top of the window
Q 48.
Mass of an object is 10 kg. What is its weight on Earth ?
Q 49.
The Earth and the Moon are attracted to each other by gravitational force. Does the Earth attract the Moon with a force that is greater or smaller or the same as the force with which the Moon attracts the Earth ? Why ?
Q 50.
Who gave three laws of planetary motion ?
