Question:
Why will a sheet of paper fall slower than one that is crumpled into a ball ?
Answer:
A sheet of paper will fall slower than the one that is crumpled into a ball. This is becausc the air offers resistance due to friction to the motion of the falling objects.The resistance offered by air to the sheet of paper is more than the resistance offered by air to the paper ball because the paper sheet has larger area.
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.
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 5.
Why do sewing needles and all pins have a sharp pointed tip?
Q 6.
What is the value of ‘g’ at the centre of Earth ?
Q 7.
Which force is responsible for tides in the ocean at night ?
Q 8.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 9.
What do you mean by acceleration due to gravity ?
Q 10.
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 11.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 12.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
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.
Who measured the value of G first time, experimentally?
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.
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.
Why is G called the Universal Constant?
Q 18.
What is the SI unit of weight ?
Q 19.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 20.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 21.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
Q 23.
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 24.
A cuboid room has dimensions 50m x 15m x 3.5m. What is the mass of the air enclosed in the room if the density of air = 1.30 kg/m
3.
Q 25.
Two bodies A and B having masses 2 kg and 4 kg respectively are separated by 2 m.Where should a body of mass 1 kg be placed so that the gravitational force on this body due to bodies A and B is zero ?
Q 26.
State the universal law of gravitation.
Q 27.
What is the importance of universal law of gravitation ?
Q 28.
Does Newton’s third law of motion apply to gravitational force ?
Q 29.
A body weighs 10 kg on the surface of earth.What would be its mass and weight at the centre of earth ?
Q 30.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 31.
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 32.
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 33.
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 34.
What do you mean by Thrust or Buoyant force?
Q 35.
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 36.
To estimate the height of a bridge over a river,a stone is dropped freely on the river from the bridge.The stone takes 2 s to touch the water surface in the river.Calculate the height of the bridge from the water level.Take g = 9.8
.
Q 37.
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 38.
Write the formula to find the magnitude of the gravitational force between the Earth and an object on the surface of the Earth.
Q 39.
Gravitational force acts on all objects in proportion to their masses.Why then,a heavy object does not fall faster than a light object ?
Q 40.
What is the acceleration of free fall ?
Q 41.
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 42.
What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?
Q 43.
Which force revolves Moon around Earth ?
Q 44.
Which force accelerates a body in free fall ?
Q 45.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
Q 46.
What is value of ‘g’ on Earth ?
Q 47.
What is the weight of a body of mass 1 kg on Earth ?
Q 48.
Can a body have weight but no mass ?
Q 49.
What is the relation between g and G ?
Q 50.
Compare gravitational force between light objects and heavy objects.
