Question:
As you climb up a mountain, your ears “pop” because of the changes in atmospheric pressure. In which direction, outward or inward, does your eardrum move when you climb up?
Answer:
Outward. Since the internal pressure of the body is higher than atmospheric pressure.
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.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 4.
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 5.
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 6.
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 7.
What do you mean by acceleration due to gravity ?
Q 8.
What do we call the gravitational force between the Earth and an object ?
Q 9.
What is the value of ‘g’ at the centre of Earth ?
Q 10.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 11.
Why do sewing needles and all pins have a sharp pointed tip?
Q 12.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 13.
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 14.
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 15.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 16.
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 17.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 18.
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 19.
What is inverse square rule ?
Q 20.
Can a body have weight but no mass ?
Q 21.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 22.
Does Newton’s third law of motion apply to gravitational force ?
Q 23.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go upwards from the earth's surface.
Q 24.
How is gravitational force of attraction between two bodies affected if(i) Mass of both bodies is doubled.(ii) Distance between them is halved.
Q 25.
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 26.
A force of 200 N acts on a surface of area 10 cm
2. Calculate thrust and pressure. How much the pressure changes if the area of contact increases to 50 cm
2.
Q 27.
The distance of planet Jupiter from the sun is 5-2 times that of Earth.Find the period of revolution of Jupiter around sun.
Q 28.
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 29.
Explain what is meant by ‘free fall’and acceleration due to gravity.
Q 30.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 31.
What are the Kepler Laws that govern the motion of the planets?
Q 32.
How gravitational force is different from or similar to magnetic force (between two magnets) or coulomb force (between two charged object)?
Q 33.
Gravitational force on the surface of the moon is only 1/6th as strong as gravitational force on the Earth. What is the weight in newtons of a 10 kg object on the moon and on the Earth? What is the value of 'g' at the surface of the moon?
Q 34.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 35.
The weight of a man is 690N which contains 5.3 x 10
-3 m
3 of blood. Find (a) blood's weight. Take density of blood is 1060 kg/m
3 (b) express it as a percentage of body weight.
Q 36.
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 37.
Mass of an object is 10 kg. What is its weight on Earth ?
Q 38.
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 39.
What is the magnitude of the gravitational force between the Earth and a 1 kg on its surface ? (Mass of the Earth Is
kg and radius of the Earth is
m.)
Q 40.
Which force revolves Moon around Earth ?
Q 41.
Which force accelerates a body in free fall ?
Q 42.
A body is projected upwards. What is its velocity at maximum height
Q 43.
How are gravitation and gravity related ?
Q 44.
Distinguish between gravitation and gravity.
Q 45.
State and explain universal law of gravitation.What is its importance ?
Q 46.
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 47.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 48.
How does value of 'g' vary on the earth? What are the factors responsible for this?
Q 49.
Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?
