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.
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.
Fill in the blanks :
Every object in the universe ________ other bodies.
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.
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.
What do we call the gravitational force between the Earth and an object ?
Q 9.
What is the value of ‘g’ at the centre of Earth ?
Q 10.
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 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.
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 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.
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 16.
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 17.
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 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.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 20.
Who measured the value of G first time, experimentally?
Q 21.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 22.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
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 24.
What is the importance of universal law of gravitation ?
Q 25.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 26.
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 27.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 28.
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 29.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 30.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 32.
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 33.
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 34.
Fill in the blanks :
The value of
g at poles is ______ (lower/higher) than its value at the equator.
Q 35.
What are Plimsoll Lines?
Q 36.
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 37.
Fill in the blanks :
Acceleration due to gravity (g) is _______ (dependent/independent) of mass.
Q 39.
Two bodies A and B having masses 2 kg and 4 kg respectively are separated by 2 m.Where should a body of mass 1 kg be placed so that the gravitational force on this body due to bodies A and B is zero ?
Q 40.
The distance between two objects is doubled. What happens to gravitational force between them
Q 41.
What is value of ‘g’ on Earth ?
Q 42.
Where is ‘g' maximum, on the surface of Earth, above the surface or below the surface of Earth ?
Q 43.
What is the weight of a body of mass 1 kg on Earth ?
Q 44.
In free fall, will heavier objects accelerate more than light ones ?
Q 45.
State and explain universal law of gravitation.What is its importance ?
Q 46.
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 47.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 48.
An object is thrown vertically upwards and rises to a height of 10 m. Calculate (i) the velocity with which the object was thrown upwards and (ii) the time taken by the object to reach the highest point.
Q 49.
State the universal law of gravitation.
Q 50.
What are the differences between the mass of an object and its weight ?
