Question:
Why does a block of plastic released under water come up to the surface of the water?
Answer:
The upward buoyant force acting on the block is greater than the downward gravitational force due to its weight. Due to this the block of plastic released under water comes up to the surface of the water.
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.
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 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.
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 6.
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 7.
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 8.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 9.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 10.
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 11.
What is the value of ‘g’ at the centre of Earth ?
Q 12.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 13.
What do you mean by acceleration due to gravity ?
Q 14.
What do we call the gravitational force between the Earth and an object ?
Q 15.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 16.
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 17.
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 18.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 19.
Which force is responsible for tides in the ocean at night ?
Q 20.
What is inverse square rule ?
Q 21.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 22.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 23.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 24.
A ball is thrown with some velocity 'u' m/s. Show that under free fall, it will fall the ground with same velocity.
Q 25.
Is weight a scalar quantity?
Q 26.
Fill in the blanks :
The average acceleration of free fall on the surface of earth is ______ .
Q 27.
Is the Archimedes principle applicable to gases?
Q 28.
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 29.
An object is thrown vertically upwards and rises to a height of 10 m. Calculate (i) the velocity with which the object was thrown upwards and (ii) the time taken by the object to reach the highest point.
Q 30.
Does Newton’s third law of motion apply to gravitational force ?
Q 31.
Then why Is the Earth not seen moving towards the stone ?
Q 32.
Fill in the blanks :
Geocentric model i.e. the Earth is the orbital centre of all celestial bodies was proposed by _____.
Q 33.
What is the gravitational force between the Earth and a body called? In which direction does it occur?
Q 34.
What are the differences between the mass of an object and its weight?
Q 35.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 36.
A ball is thrown upwards from the ground of a tower with a speed of 20 m/s. There is a window in the tower at the height of 15m from ground. How many times and when will the ball pass the window? (g = 10 m/s
2)
Q 37.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
Q 38.
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 40.
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Q 41.
A force of 20 N acts upon a body whose weight is 9.8 N.What is the mass of the body and how much is its acceleration ?
Q 42.
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 43.
What is the importance of universal law of gravitation ?
Q 44.
Can a body have weight but no mass ?
Q 45.
Write down the equations of motion of objects under the influence of gravitational force of Earth.Explain the meaning of the symbols used.
Q 46.
Explain what is meant by ‘free fall’and acceleration due to gravity.
Q 47.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 48.
Fill in the blanks :
The mass of the earth is ________ kg.
Q 49.
What is retrograde motion of planets (say mars planet)?
Q 50.
Why is G called the Universal Constant?
