Question:
State Archimedes’ Principle. Based on this principle, write its two applications.
Answer:
When a body is partially or wholly immersed in a fluid, it experiences an upthrust and apparently loses its weight which is equal to the weight of the fluid displaced by the immersed part of the body.
Applications based on Archimedes’ principle are:
- designing of ships and submarines
- Lactometers, which are used to determine the purity of a sample of milk
- hydrometers used for determining the density of liquids
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.
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 4.
What do we call the gravitational force between the Earth and an object ?
Q 5.
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 6.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 7.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 8.
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 9.
Why do sewing needles and all pins have a sharp pointed tip?
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 do you mean by acceleration due to gravity ?
Q 12.
What is the value of ‘g’ at the centre of Earth ?
Q 13.
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 14.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 15.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 16.
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 17.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 18.
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 19.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 20.
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 21.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 22.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 23.
Can a body have weight but no mass ?
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.
Distinguish between gravitation and gravity.
Q 26.
Who measured the value of G first time, experimentally?
Q 27.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 28.
Why does an object float or sink when placed on the surface of the water?
Q 29.
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 30.
Which force is responsible for tides in the ocean at night ?
Q 31.
Explain what is meant by ‘free fall’and acceleration due to gravity.
Q 32.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 33.
Does Law of gravitation obey Newton's third law of motion?
Q 34.
Define weight? How it is related to mass?
Q 35.
Write the standard equations in the form when an object is dropped from a height?
Q 36.
Fill in the blanks :
The average acceleration of free fall on the surface of earth is ______ .
Q 37.
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 38.
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Q 39.
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Q 40.
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?
Q 41.
Is the Archimedes principle applicable to gases?
Q 42.
Loaded test-tube placed in pure milk sinks to a certain mark (M). Now some water is mixed with the milk. Will the test tube sink more or less? Explain.
Q 43.
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 44.
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 45.
Write the formula to find the magnitude of the gravitational force between the Earth and an object on the surface of the Earth.
Q 46.
What do you mean by free fall ?
Q 47.
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 48.
What is the importance of universal law of gravitation ?
Q 49.
Two objects of masses
having the same size are dropped simultaneously from heights
respectively.Find out the ratio of time they would take in reaching the ground.Will this ratio remain the same if (1) one of the objects is hollow and the other one is solid and (ii) both of them are hollow,size remaining the same in each case.Give reason.
Q 50.
Which force revolves Moon around Earth ?
