Question:
Is acceleration due to gravity a vector or a scalar? Write its S.I. unit.
Answer:
It is a vector quantity and hence has both magnitude and direction. The SI unit is m/s2.
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.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 4.
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 5.
Fill in the blanks :
Every object in the universe ________ other bodies.
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.
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 9.
What do we call the gravitational force between the Earth and an object ?
Q 10.
What is the value of ‘g’ at the centre of Earth ?
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.
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 13.
What do you mean by acceleration due to gravity ?
Q 14.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 15.
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 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.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 18.
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 19.
Who measured the value of G first time, experimentally?
Q 20.
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 21.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 22.
What is the importance of universal law of gravitation ?
Q 23.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 24.
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 25.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 27.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 28.
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 29.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 31.
Fill in the blanks :
The value of
g at poles is ______ (lower/higher) than its value at the equator.
Q 32.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 33.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 34.
What was geocentric model? Who proposed this theory?
Q 35.
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 36.
A car falls off a ledge and drops to the ground in 0.5 s.Let g =
(for simplifying the calculations).
(i) What is its speed on striking the ground ?
(ii) What is its average speed during 0.5 s ?
(iii) How high is the ledge from the ground ?
Q 37.
Who explained the motion of planets around the Sun ?
Q 38.
State and explain universal law of gravitation.What is its importance ?
Q 39.
Take a piece of thread.Tie a small piece of stone to one end of the thread. Hold the other end of the thread in hand and whirl it round.Note the motion of the stone.If the thread breaks suddenly,the stone flies off along tangent to the circle at that instant.
Read the above passage and answer the following questions:
(i) Which force Is whirling the stone ? Who is providing this force ?
(ii) Why does the stone fly off along the tangent to the circle at that instant ?
(iii) What values of life do you learn from this ?
Q 40.
Fill in the blanks :
According to the Heliocentric theory, the _____ is at centre and _______ move around it.
Q 41.
Fill in the blanks :
______ stated that every planet moves around the sun in closed elliptical orbit, with the ___ at one focus.
Q 42.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 43.
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 44.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go upwards from the earth's surface.
Q 45.
Does Law of gravitation obey Newton's third law of motion?
Q 46.
(a) What is the relationship between g and G?
(b) Show mathematically whether g (acceleration due to gravity on the earth) depends on the mass of the object itself or not.
(c) Show that for a given location on the surface of the earth g is almost constant.
Q 47.
Define weight? How it is related to mass?
Q 48.
Fill in the blanks :
Motion of body with constant speed in a circular path is called ______________.
Q 49.
Fill in the blanks :
It is the ____________ of the earth, which holds our atmosphere in place.
Q 50.
Fill in the blanks :
The force of gravity _________ with altitude. It also varies on the surface of the earth, _________ from poles to the equator.
