Question:
Distinguish between mass and weight.
Answer:
Refer to Arts 3.17 and 3.18,Pages 162 and 163.
Gravitation
Q 1.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 2.
Two objects of masses
having the same size are dropped simultaneously from heights
respectively.Find out the ratio of time they would take in reaching the ground.Will this ratio remain the same if (1) one of the objects is hollow and the other one is solid and (ii) both of them are hollow,size remaining the same in each case.Give reason.
Q 3.
What is the SI unit of weight ?
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.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 7.
Why do sewing needles and all pins have a sharp pointed tip?
Q 8.
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 9.
What do you mean by acceleration due to gravity ?
Q 10.
Two particles of equal mass (m) move in a circle of radius (r) under the action of their mutual gravitational attraction. Find the speed of each particle.
Q 11.
A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground.
Q 12.
What are the differences between the mass of an object and its weight ?
Q 13.
How are gravitation and gravity related ?
Q 14.
State and explain universal law of gravitation.What is its importance ?
Q 15.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 16.
Fill in the blanks :
All other variables remaining constant, the force of gravitation is ________ proportional to the square of distance between the two objects.
Q 17.
The mass of Sun is
kg and mass of Earth is
kg. If the distance between the centres of Sun and Earth is
km,calculate the force of gravitation between them.
Q 18.
Does gravitational force between two objects depend on medium between them ?
Q 19.
Does value of ‘g’ vary from place to place on Earth ?
Q 20.
Distinguish between mass and weight.
Q 21.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go upwards from the earth's surface.
Q 22.
Define 'g' or acceleration due to gravity? Does it depend on the mass of the body (near the surface of the earth)experiencing 'g'?
Q 23.
A ball is thrown up and is caught by the player after 4 seconds.How high did it go and with what velocity was it thrown? How far below the ball will be from its highest point after 3 seconds from start?
Q 25.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 26.
The following figure shows four containers containing a liquid at the same height. Rank them according to the pressure exerted by the liquid on the bottom of the containers in ascending order.
a. 1, 2, 3, 4 b. 4. 3, 1, 2 c. 3, 4, 1, 2 d. same pressure in each case.
Q 28.
State Archimedes’ Principle. Based on this principle, write its two applications.
Q 29.
A solid weighs 80g in air, 64g in water. Calculate the relative density of solid.
Q 30.
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 31.
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 32.
How does the force of gravitation between two objects change when the distance between them is reduced to half ?
Q 33.
What is the acceleration of free fall ?
Q 34.
What do we call the gravitational force between the Earth and an object ?
Q 35.
What is the value of G (i) on Earth (ii) on Moon ?
Q 36.
In free fall, will heavier objects accelerate more than light ones ?
Q 37.
On earth,value of G =
.What is its value on moon,where g is nearly
th that of earth ?
Q 38.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 39.
Fill in the blanks :
According to the Heliocentric theory, the _____ is at centre and _______ move around it.
Q 40.
Fill in the blanks :
The force which keeps the object moving in a circular path is called _____ force. It always acts towards the _____.
Q 41.
Fill in the blanks :
The mass of the earth is ________ kg.
Q 42.
Fill in the blanks :
The mass of an object _____ (varies/does not vary) on the earth as well as on the moon. But its weight is ______(same/different) on both places.
Q 43.
Why is G called the Universal Constant?
Q 44.
An object moves in a circular motion due to centripetal force, acting towards the center. The moon also rotates around the earth? Does centripetal force acts on it? Why does the moon not fall on the earth?
OR
Q:If the moon attracts the earth, why does the earth not move towards the moon?
Q 45.
How gravitational force is different from or similar to magnetic force (between two magnets) or coulomb force (between two charged object)?
Q 46.
A ball is thrown with some velocity 'u' m/s. Show that under free fall, it will fall the ground with same velocity.
Q 47.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 48.
What are the factors the buoyant force depends on?
Q 49.
Is the Archimedes principle applicable to gases?
Q 50.
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.
