Question:
A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?
Answer:
Given, initial velocity (u) = 40 m/s
Final velocity when stone reaches at max. height (v) = 0 m/s
Acceleration due gravity in upward motion of stone g = -9.8 m/s2
g is taken -ve because it opposed the vertical motion.
max. height the stone will reach (h) = ?
Using equation v2 - u2 =2aS,
⇒ 0 - u2 = -2gh
⇒ h = u2/(2g) = (40)2/(2 × 10) = 80m
It means the stone will reach upto 80m height and then it comes back to ground(original position).
Total Distance covered by stone = 2 × 80 = 160m
Net displacement = Upward Displacement + Downward Displacement = 80 + (-80) = 0m
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.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 4.
What do we call the gravitational force between the Earth and an object ?
Q 5.
What is the value of ‘g’ at the centre of Earth ?
Q 6.
What do you mean by acceleration due to gravity ?
Q 7.
Why do sewing needles and all pins have a sharp pointed tip?
Q 8.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
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.
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 11.
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 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.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 14.
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 15.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 16.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 17.
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 18.
Is weight a scalar quantity?
Q 19.
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 20.
Define g and G.Establish relation between them.
Q 21.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 22.
Define weight? How it is related to mass?
Q 23.
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 25.
Is mass a scalar quantity?
Q 27.
Fill in the blanks :
The SI unit of mass is ______.
Q 28.
The volume of 50 g of a substance is 20 cm
3. If the density of water is 1 g cm
-3, will the substance float or sink?
Q 29.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 30.
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 31.
Fill in the blanks :
According to the Heliocentric theory, the _____ is at centre and _______ move around it.
Q 32.
Fill in the blanks :
Acceleration due to gravity (g) is _______ (dependent/independent) of mass.
Q 33.
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 34.
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.
Q 35.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 36.
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 37.
Why will a sheet of paper fall slower than one that is crumpled into a ball?
Q 38.
As you climb up a mountain, your ears “pop” because of the changes in atmospheric pressure. In which direction, outward or inward, does your eardrum move when you climb up?
Q 39.
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 40.
What is the acceleration of free fall ?
Q 41.
Why will a sheet of paper fall slower than one that is crumpled into a ball ?
Q 42.
The distance between two objects is doubled. What happens to gravitational force between them
Q 43.
Does gravitational force between two objects depend on medium between them ?
Q 44.
Who gave three laws of planetary motion ?
Q 45.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
Q 46.
Then why Is the Earth not seen moving towards the stone ?
Q 47.
What is value of ‘g’ on Earth ?
Q 48.
What is the SI unit of weight ?
Q 49.
Can a body have weight but no mass ?
Q 50.
How are gravitation and gravity related ?
