Question:
A ball of mass 4kg and density 4000 kgm3 is completely immersed in water. Find the buoyant force acting on ball if the density of water is 103kg/m3. (Take g = 10ms-2)
Answer:
Volume of water displaced = Volume of ball = mass ÷ density
= 4 ÷ 4000 = 10 -3m3.
Buoyant force = Weight of water displaced
= Mass of water displaced x g
= Volume of water displaced x density of water x g
= 10 -3m3 x 103kg/m3 x 10
= 10 N
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 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 4.
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 5.
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 6.
Calculate the value of acceleration due to gravity on Moon. Given mass of Moon =
kg, radius of Moon = 1740 km
Q 7.
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 8.
Fill in the blanks :
Every object in the universe ________ other bodies.
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.
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.
What do you mean by acceleration due to gravity ?
Q 13.
Which force is responsible for tides in the ocean at night ?
Q 14.
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 15.
What do we call the gravitational force between the Earth and an object ?
Q 16.
State and explain universal law of gravitation given by Newton.What is the importance of this law
Q 17.
Fill in the blanks :
________ of an object is the force of gravity acting on it.
Q 18.
Can you calculate density of Earth from Newton’s law of gravitation ?
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.
Fill in the blanks :
Heliocentric model was proposed by ______.
Q 21.
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 22.
Fill in the blanks :
The value of
g at poles is ______ (lower/higher) than its value at the equator.
Q 23.
What happens to 'g' experienced by a body when it moves up the earth's surface?
Q 24.
What are the differences between the mass of an object and its weight?
Q 25.
Write the standard equations of motion when an object is thrown upwards with some initial velocity?
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.
Why is the weight of an object on the Moon (l/6)th its weight on the Earth ?
Q 28.
A stone is thrown vertically upward with an initial velocity of 40 m/s.Taking g =
,find the maximum height reached by the stone.What is the net displacement and the total distance covered by the stone ?
Q 29.
The distance between two objects is doubled. What happens to gravitational force between them
Q 30.
Who measured the value of G first time, experimentally?
Q 31.
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 32.
Mass of an object is 10 kg. What is its weight on the Earth? (g = 9.8 m/s
2.)
Q 33.
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 35.
The pressure at the bottom of a filled glass (density = 1000 kg/m
3) of water is P. The water is taken out and the glass is filled with kerosene oil (density = 817.5 kg/m
3). Now the pressure at the bottom will be a. same as P b. smaller than P c. larger than P d. cannot be determined.
Q 36.
The volume of a 500 g sealed packet is 350 cm
3. Will the packet float or sink in water if the density of water is 1 g cm
-3? What will be the mass of the water displaced by this packet?
Q 37.
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 38.
What is the gravitational acceleration of a spaceship at a distance equal to two Earth’s radius from the centre of the Earth ?
Q 39.
Write the formula to find the magnitude of the gravitational force between the Earth and an object on the surface of the Earth.
Q 40.
What are the differences between the mass of an object and its weight ?
Q 41.
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 42.
What is the importance of universal law of gravitation ?
Q 43.
What is the acceleration of free fall ?
Q 44.
Which force revolves Moon around Earth ?
Q 45.
Does Newton’s third law of motion apply to gravitational force ?
Q 46.
A stone falling towards Earth also attracts the Earth with the same force.Is it true ?
Q 47.
What is value of ‘g’ on Earth ?
Q 48.
Where is ‘g’greater, at poles or at equator ?
Q 49.
A body is just dropped from a height What is its initial velocity ?
Q 50.
Why don’t two objects move towards each other due to gravitational pull between them ?
