Question:
A body is just dropped from a height What is its initial velocity ?
Answer:
Initial velocity of a body when dropped from a height is zero, i.e.. u = 0.
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.
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.
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 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.
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 7.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 8.
What is the value of ‘g’ at the centre of Earth ?
Q 9.
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 10.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 11.
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 12.
What do you mean by acceleration due to gravity ?
Q 13.
What do we call the gravitational force between the Earth and an object ?
Q 14.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 15.
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 16.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 17.
Which force is responsible for tides in the ocean at night ?
Q 18.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 19.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 20.
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 21.
What is the importance of universal law of gravitation ?
Q 22.
Why is G called the Universal Constant?
Q 23.
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 24.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 25.
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 26.
Why don’t two objects move towards each other due to gravitational pull between them ?
Q 27.
Can a body have weight but no mass ?
Q 28.
Can you calculate density of Earth from Newton’s law of gravitation ?
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.
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 31.
What is the gravitational force between the Earth and a body called? In which direction does it occur?
Q 32.
How does value of 'g' vary on the earth? What are the factors responsible for this?
Q 33.
Fill in the blanks :
During free fall condition, the body is in state of __________.
Q 34.
What do you mean by Thrust or Buoyant force?
Q 35.
Is the Archimedes principle applicable to gases?
Q 36.
If the distance between two masses is increased by a factor of 4,by what factor would the mass of one of them have to be altered to maintain the same gravitational force ?
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.
What is the source of centripetal force that a planet requires to revolve around the Sun ? On what factors does that force depend ?
Q 39.
Which force revolves Moon around Earth ?
Q 40.
Does Newton’s third law of motion apply to gravitational force ?
Q 41.
What is value of ‘g’ on Earth ?
Q 42.
Distinguish between gravitation and gravity.
Q 43.
State and explain universal law of gravitation.What is its importance ?
Q 44.
Write down the equations of motion of objects under the influence of gravitational force of Earth.Explain the meaning of the symbols used.
Q 45.
On earth,value of G =
.What is its value on moon,where g is nearly
th that of earth ?
Q 46.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 47.
Fill in the blanks :
Kepler's Law of ______ states that a line that connects a planet to the Sun sweeps out equal ______ in the plane of the planet's orbit in _____time intervals.
Q 48.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 49.
What was heliocentric theory? Who proposed this?
Q 50.
An object is placed at the surface of the earth and is at distance R from the center of the earth. The object weighs 180N. What will be its weight if it is at distance 3R from the center of the earth.
