Question:
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 ?
Answer:
Here,u = 40 m/s,g = -,h = ?,v = 0
From =2 gh,0- = 2(- 10) h or h = = 80 m
As final position of the stone coincides with its initial position,net displacement = 0.
Total distance covered by the stone = h+h = 2h = 2x80m = 160 m
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
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 3.
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 4.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 5.
Which force is responsible for tides in the ocean at night ?
Q 6.
What is the value of ‘g’ at the centre of Earth ?
Q 7.
Why do sewing needles and all pins have a sharp pointed tip?
Q 8.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 9.
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 10.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 11.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 12.
What do you mean by acceleration due to gravity ?
Q 13.
Who measured the value of G first time, experimentally?
Q 14.
The mass of Earth is
kg and that of moon is
kg. If the distance between the Earth and the Moon is
km, calculate the force exerted by Earth on the Moon. Given G =
.
Q 15.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 16.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 17.
Calculate the force of gravitation between two objects of masses 80 kg and 1200 kg kept at a distance of 10 m from eachother.Given, G =
/
.
Q 18.
What is the SI unit of weight ?
Q 19.
Fill in the blanks :
The SI unit of mass is ______.
Q 20.
Why will a sheet of paper fall slower than one that is crumpled into a ball?
Q 21.
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 22.
What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?
Q 23.
Which force revolves Moon around Earth ?
Q 24.
Who gave three laws of planetary motion ?
Q 25.
What is the SI unit of mass ?
Q 26.
Name two applications of Newton’s law of gravitation.
Q 27.
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 28.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 29.
What was geocentric model? Who proposed this theory?
Q 30.
An object is placed at the surface of the earth and is at distance R from the center of the earth. The object weighs 180N. What will be its weight if it is at distance 3R from the center of the earth.
Q 31.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
Q 32.
In what direction does the buoyant force on an object immersed in a liquid act?
Q 33.
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Q 34.
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 35.
What do we call the gravitational force between the Earth and an object ?
Q 36.
Who explained the motion of planets around the Sun ?
Q 37.
Does Newton’s third law of motion apply to gravitational force ?
Q 38.
Does value of ‘g’ vary from place to place on Earth ?
Q 39.
Where is ‘g’greater, at poles or at equator ?
Q 40.
Can a body have weight but no mass ?
Q 41.
Distinguish between gravitation and gravity.
Q 42.
Take a piece of thread.Tie a small piece of stone to one end of the thread. Hold the other end of the thread in hand and whirl it round.Note the motion of the stone.If the thread breaks suddenly,the stone flies off along tangent to the circle at that instant.
Read the above passage and answer the following questions:
(i) Which force Is whirling the stone ? Who is providing this force ?
(ii) Why does the stone fly off along the tangent to the circle at that instant ?
(iii) What values of life do you learn from this ?
Q 43.
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 44.
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 45.
A ball is thrown with some velocity 'u' m/s. Show that under free fall, it will fall the ground with same velocity.
Q 47.
Why does one feel giddy while moving on a merry go round ?
Q 48.
Fill in the blanks :
A body is said to be in _______ when only gravity acts on it.
Q 49.
Fill in the blanks :
During free fall condition, the body is in state of __________.
Q 50.
Fill in the blanks :
All other variables remaining constant, the force of gravitation is ________ proportional to the square of distance between the two objects.
