Question:
A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground.
Answer:
Given initial velocity (u) = 0 m/s
Final velocity (v) = ?
height (distance) h = 19.6 m
acceleration due to gravity (g) = +9.8 m/s2.
g is taken as +ve because it will accelerate the vertical motion.
Using equation v2 - u2 =2aS, ⇒ v2- 0 = 2gh
⇒ v2 = 2 × 9.8 × 19.6 = (19.6)2
⇒ v = 19.6 m/s
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.
What do we call the gravitational force between the Earth and an object ?
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.
Can you calculate density of Earth from Newton’s law of gravitation ?
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.
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.
What is the value of ‘g’ at the centre of Earth ?
Q 10.
Why do sewing needles and all pins have a sharp pointed tip?
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.
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.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 15.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
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.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 18.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 19.
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 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.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 22.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 23.
Can a body have weight but no mass ?
Q 24.
Who measured the value of G first time, experimentally?
Q 25.
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 26.
Which force is responsible for tides in the ocean at night ?
Q 27.
How are gravitation and gravity related ?
Q 28.
Distinguish between gravitation and gravity.
Q 29.
Fill in the blanks :
______ stated that every planet moves around the sun in closed elliptical orbit, with the ___ at one focus.
Q 30.
Fill in the blanks :
The force which keeps the object moving in a circular path is called _____ force. It always acts towards the _____.
Q 31.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go upwards from the earth's surface.
Q 32.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 33.
Why does an object float or sink when placed on the surface of the water?
Q 34.
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 35.
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 36.
What is the value of G (i) on Earth (ii) on Moon ?
Q 37.
State and explain universal law of gravitation.What is its importance ?
Q 38.
Explain what is meant by ‘free fall’and acceleration due to gravity.
Q 39.
On earth,value of G =
.What is its value on moon,where g is nearly
th that of earth ?
Q 40.
In Fig.,the line that joins a planet to the sun sweeps out areas
,
in time intervals 6 weeks,3 weeks and 2 weeks respectively.How are
,
realted ?
Q 41.
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 42.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 43.
What is the gravitational force between the Earth and a body called? In which direction does it occur?
Q 44.
Does the force of attraction between two objects depend on the properties of intervening medium?
Q 45.
Does Law of gravitation obey Newton's third law of motion?
Q 46.
How does value of 'g' vary on the earth? What are the factors responsible for this?
Q 47.
Define weight? How it is related to mass?
Q 48.
Write the standard equations in the form when an object is dropped from a height?
Q 49.
A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate(i) the maximum height to which it rises.(ii)the total time it takes to return to the surface of the earth.
Q 50.
A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s
2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?
