Question:
A body weighs 10 kg on the surface of earth.What would be its mass and weight at the centre of earth ?
Answer:
Here,at the surface of earth, W = 10 kg wt Mass of body = 10 kg.
At the centre of earth,mass, m = 10 kg,as it remains unaffected.
Since g = 0,therefore,W = mg = 10 x 0 = Zero.
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
Why do sewing needles and all pins have a sharp pointed tip?
Q 3.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 4.
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 5.
What is the value of ‘g’ at the centre of Earth ?
Q 6.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 7.
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 8.
Which force is responsible for tides in the ocean at night ?
Q 9.
What do you mean by acceleration due to gravity ?
Q 10.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 11.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 12.
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 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.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 15.
What do we call the gravitational force between the Earth and an object ?
Q 16.
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 17.
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 18.
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 19.
Who measured the value of G first time, experimentally?
Q 20.
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 21.
What is the importance of universal law of gravitation ?
Q 22.
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 23.
Fill in the blanks :
Assuming negligible air drag, if a steel ball and a table tennis ball are dropped from a height of 100 metres, both will reach the ground at ________ time(s). (same/different)
Q 24.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 25.
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 26.
A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet
Q 27.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 28.
Fill in the blanks :
The force of gravity _________ with altitude. It also varies on the surface of the earth, _________ from poles to the equator.
Q 29.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 30.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 31.
Where is ‘g' maximum, on the surface of Earth, above the surface or below the surface of Earth ?
Q 32.
Is weight a scalar quantity?
Q 35.
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 36.
What are the factors the buoyant force depends on?
Q 37.
A car falls off a ledge and drops to the ground in 0.5 s.Let g =
(for simplifying the calculations).
(i) What is its speed on striking the ground ?
(ii) What is its average speed during 0.5 s ?
(iii) How high is the ledge from the ground ?
Q 38.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
Q 39.
Then why Is the Earth not seen moving towards the stone ?
Q 40.
Where is ‘g’greater, at poles or at equator ?
Q 41.
What is the weight of a body of mass 1 kg on Earth ?
Q 42.
Fill in the blanks :
Kepler's Law of ______ states that a line that connects a planet to the Sun sweeps out equal ______ in the plane of the planet's orbit in _____time intervals.
Q 43.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 44.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 45.
Fill in the blanks :
The value of G was found out by _______ by using a ________.
Q 46.
What was geocentric model? Who proposed this theory?
Q 47.
What is the gravitational force between the Earth and a body called? In which direction does it occur?
Q 48.
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 49.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 50.
Why is the weight of an object on the moon 1/6th its weight on the earth?
