Question:
What are Plimsoll Lines?
Answer:
While loading a ship, care is taken it should not be loaded too much. Its load depends on the density of the sea in which it floats. The ship would sink if its load exceeds. To indicate the depth up to which the ship can sink in a sea of different densities under different climatic conditions, several lines are marked on the sides of the ship. It ensures stability and safety of the ship and these lines are called Plimsoll lines (name after sailor Captain Plimsoll) .
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.
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 9.
What is the value of ‘g’ at the centre of Earth ?
Q 10.
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 11.
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 12.
What do we call the gravitational force between the Earth and an object ?
Q 13.
What do you mean by acceleration due to gravity ?
Q 14.
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 15.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 16.
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 17.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 18.
Who measured the value of G first time, experimentally?
Q 19.
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 20.
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 21.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 22.
What is the importance of universal law of gravitation ?
Q 23.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 24.
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 25.
Fill in the blanks :
Heliocentric model was proposed by ______.
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.
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 29.
Fill in the blanks :
Weight of an object is the product of ______ and ________.
Q 30.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 32.
What was geocentric model? Who proposed this theory?
Q 33.
Fill in the blanks :
The gravitational force between the earth and the object is generally called ____________.
Q 34.
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 35.
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 36.
Who explained the motion of planets around the Sun ?
Q 37.
Fill in the blanks :
The value of
g at poles is ______ (lower/higher) than its value at the equator.
Q 38.
Define weight? How it is related to mass?
Q 39.
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 40.
Does Newton’s third law of motion apply to gravitational force ?
Q 41.
What is the SI unit of weight ?
Q 42.
State and explain universal law of gravitation.What is its importance ?
Q 43.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go upwards from the earth's surface.
Q 44.
(a) What is the relationship between g and G?
(b) Show mathematically whether g (acceleration due to gravity on the earth) depends on the mass of the object itself or not.
(c) Show that for a given location on the surface of the earth g is almost constant.
Q 45.
Is weight a scalar quantity?
Q 46.
Fill in the blanks :
Motion of body with constant speed in a circular path is called ______________.
Q 47.
Fill in the blanks :
It is the ____________ of the earth, which holds our atmosphere in place.
Q 48.
The weight of a man is 690N which contains 5.3 x 10
-3 m
3 of blood. Find (a) blood's weight. Take density of blood is 1060 kg/m
3 (b) express it as a percentage of body weight.
Q 50.
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?
