Question:
What do you mean by Thrust or Buoyant force?
Answer:
The upward force exerted by a liquid when a body is immersed in the liquid is called thrust or Buoyant Force.
Note: When in equilibrium the buoyant force is balanced by the weight of an object or the force of gravity acting on it.
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
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 3.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 4.
Why do sewing needles and all pins have a sharp pointed tip?
Q 5.
What is the value of ‘g’ at the centre of Earth ?
Q 6.
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 7.
Which force is responsible for tides in the ocean at night ?
Q 8.
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 9.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 10.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 11.
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 12.
What do we call the gravitational force between the Earth and an object ?
Q 13.
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 14.
What do you mean by acceleration due to gravity ?
Q 15.
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 16.
What is the importance of universal law of gravitation ?
Q 17.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 18.
What is value of ‘g’ on Earth ?
Q 19.
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 20.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 21.
Who measured the value of G first time, experimentally?
Q 22.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 23.
Distinguish between mass and weight.
Q 24.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 25.
A body is projected upwards. What is its velocity at maximum height
Q 27.
Fill in the blanks :
Universal gravitational constant G = _____________.
Q 28.
Why does a block of plastic released under water come up to the surface of the water?
Q 29.
A stone drops from the edge of the roof.It passes a window 2 m high in 0.1 s.How far is the roof above the top of the window
Q 30.
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 31.
Fill in the blanks :
When objects of different masses and sizes are dropped from same height would reach the ground at ______ (same time/different times), considering negligible air resistance.
Q 32.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go downwards from the earth's surface.
Q 33.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 34.
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 35.
Why will a sheet of paper fall slower than one that is crumpled into a ball?
Q 36.
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 37.
What is the SI unit of weight ?
Q 38.
Can a body have mass but no weight ?
Q 39.
Write down the equations of motion of objects under the influence of gravitational force of Earth.Explain the meaning of the symbols used.
Q 40.
Why is G called the Universal Constant?
Q 42.
Is mass a scalar quantity?
Q 43.
Is weight a scalar quantity?
Q 44.
What is weightlessness?
Q 45.
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 46.
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 47.
What do you mean by Thrust or Buoyant force?
Q 48.
What are Plimsoll Lines?
Q 49.
Relative density of silver is 10.8. If the density of water is 10
3kg/m
3, find density of silver.
Q 50.
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 ?
