Question:
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.
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.
What do we call the gravitational force between the Earth and an object ?
Q 4.
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 5.
Is weight a scalar quantity?
Q 6.
What is the value of ‘g’ at the centre of Earth ?
Q 7.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 8.
What do you mean by acceleration due to gravity ?
Q 9.
The distance between two objects is doubled. What happens to gravitational force between them
Q 10.
Why do sewing needles and all pins have a sharp pointed tip?
Q 11.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 12.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 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.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 15.
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Q 16.
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 17.
Fill in the blanks :
Geocentric model i.e. the Earth is the orbital centre of all celestial bodies was proposed by _____.
Q 18.
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 19.
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 20.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 21.
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 22.
Then why Is the Earth not seen moving towards the stone ?
Q 23.
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 24.
Fill in the blanks :
Acceleration due to gravity (g) is _______ (dependent/independent) of mass.
Q 25.
What are the Kepler Laws that govern the motion of the planets?
Q 26.
Who measured the value of G first time, experimentally?
Q 27.
What is the gravitational force between the Earth and a body called? In which direction does it occur?
Q 28.
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 29.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 30.
(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 31.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 32.
Define weight? How it is related to mass?
Q 33.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 34.
Name the scientist who identified the relation about force of gravitation. Name the law.
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.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 38.
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Q 39.
The weight of an empty glass is 1 N. When completely filled with water, the glass weighs 4 N. If you now throw the water away and fill the glass partly with sand, the weight becomes 4 N. If the rest of the glass is now filled up with water, the weight becomes 6 N. What is the relative density of sand?
Q 40.
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 41.
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 42.
State the universal law of gravitation.
Q 43.
What is the acceleration of free fall ?
Q 44.
What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?
Q 45.
Who gave three laws of planetary motion ?
Q 46.
Who explained the motion of planets around the Sun ?
Q 47.
Does Newton’s third law of motion apply to gravitational force ?
Q 48.
What is the weight of a body of mass 1 kg on Earth ?
Q 49.
Can a body have weight but no mass ?
Q 50.
State Kepler’s Laws of planetary motion.
