Question:
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Answer:
Pressure = Force/Area
⇒ Pressure is inversely proportional to the surface area on which the force acts.
Since the contact surface area of a thin string, strap is very small, it exerts larger pressure on the shoulder.
Gravitation
Q 1.
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 2.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 3.
What do we call the gravitational force between the Earth and an object ?
Q 4.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 5.
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 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.
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 8.
What do you mean by acceleration due to gravity ?
Q 9.
What is the value of ‘g’ at the centre of Earth ?
Q 10.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 11.
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 12.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 13.
Why do sewing needles and all pins have a sharp pointed tip?
Q 14.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 15.
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 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.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 19.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 20.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 21.
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 22.
What is inverse square rule ?
Q 23.
Can a body have weight but no mass ?
Q 24.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go upwards from the earth's surface.
Q 25.
Is weight a scalar quantity?
Q 26.
A force of 200 N acts on a surface of area 10 cm
2. Calculate thrust and pressure. How much the pressure changes if the area of contact increases to 50 cm
2.
Q 27.
Which force is responsible for tides in the ocean at night ?
Q 28.
Does Newton’s third law of motion apply to gravitational force ?
Q 29.
Explain what is meant by ‘free fall’and acceleration due to gravity.
Q 30.
Who measured the value of G first time, experimentally?
Q 31.
How gravitational force is different from or similar to magnetic force (between two magnets) or coulomb force (between two charged object)?
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.
Define weight? How it is related to mass?
Q 34.
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 36.
Fill in the blanks :
The force of gravity _________ with altitude. It also varies on the surface of the earth, _________ from poles to the equator.
Q 37.
The volume of a 500 g sealed packet is 350 cm
3. Will the packet float or sink in water if the density of water is 1 g cm
-3? What will be the mass of the water displaced by this packet?
Q 38.
The weight of an empty glass is 1 N. When completely filled with water, the glass weighs 4 N. If you now throw the water away and fill the glass partly with sand, the weight becomes 4 N. If the rest of the glass is now filled up with water, the weight becomes 6 N. What is the relative density of sand?
Q 39.
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 40.
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 41.
The Earth and the Moon are attracted to each other by gravitational force. Does the Earth attract the Moon with a force that is greater or smaller or the same as the force with which the Moon attracts the Earth ? Why ?
Q 42.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 43.
Fill in the blanks :
The value of
g at poles is ______ (lower/higher) than its value at the equator.
Q 44.
What are the Kepler Laws that govern the motion of the planets?
Q 45.
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 46.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 47.
Gravitational force on the surface of the moon is only 1/6th as strong as gravitational force on the Earth. What is the weight in newtons of a 10 kg object on the moon and on the Earth? What is the value of 'g' at the surface of the moon?
Q 48.
A ball is thrown upwards from the ground of a tower with a speed of 20 m/s. There is a window in the tower at the height of 15m from ground. How many times and when will the ball pass the window? (g = 10 m/s
2)
Q 50.
The tangential velocity of a planet or moon moving in a circle is at a right angle to ____________. (fill in the blank)
