Question:
The volume of 50 g of a substance is 20 cm3. If the density of water is 1 g cm-3, will the substance float or sink?
Answer:
Given, mass of the substance (m) = 50g
volume of the substance (v) = 20 cm3
Density of the substance = m/v = 50/20 = 2.5 g/cm3
Since the density of a substance is more than the density of water, the substance will sink.
Gravitation
Q 1.
State Kepler’s Laws of planetary motion. How did Newton guess inverse square law ?
Q 2.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 3.
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 4.
Why do sewing needles and all pins have a sharp pointed tip?
Q 5.
What is the value of ‘g’ at the centre of Earth ?
Q 6.
Fill in the blanks :
Every object in the universe ________ other bodies.
Q 7.
What do you mean by acceleration due to gravity ?
Q 8.
Which force is responsible for tides in the ocean at night ?
Q 9.
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 10.
Can you calculate density of Earth from Newton’s law of gravitation ?
Q 11.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 12.
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 13.
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 14.
What do we call the gravitational force between the Earth and an object ?
Q 15.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 16.
Who measured the value of G first time, experimentally?
Q 17.
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 18.
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 19.
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 20.
What is the importance of universal law of gravitation ?
Q 21.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 22.
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 23.
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 24.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 26.
Is weight a scalar quantity?
Q 27.
What are Plimsoll Lines?
Q 28.
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 30.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 31.
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 32.
What is value of ‘g’ on Earth ?
Q 33.
Fill in the blanks :
The value of
g on the earth's surface is ______.
Q 34.
Fill in the blanks :
The value of
g ________ (increases/decreases) as we go downwards from the earth's surface.
Q 35.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
Q 36.
State and explain universal law of gravitation.What is its importance ?
Q 37.
Why is G called the Universal Constant?
Q 38.
What do you mean by Thrust or Buoyant force?
Q 39.
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 40.
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 41.
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 42.
State the universal law of gravitation.
Q 43.
Then why Is the Earth not seen moving towards the stone ?
Q 44.
Why don’t two objects move towards each other due to gravitational pull between them ?
Q 45.
Fill in the blanks :
The value of Universal Gravitation constant (G) is ________ Nm
2kgs
-2.
Q 46.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 47.
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 48.
A ball of mass 4kg and density 4000 kgm
3 is completely immersed in water. Find the buoyant force acting on ball if the density of water is 10
3kg/m
3. (Take g = 10ms
-2)
Q 49.
A stone drops from the edge of the roof.It passes a window 2 m high in 0.1 s.How far is the roof above the top of the window
Q 50.
To estimate the height of a bridge over a river,a stone is dropped freely on the river from the bridge.The stone takes 2 s to touch the water surface in the river.Calculate the height of the bridge from the water level.Take g = 9.8
.
