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प्रश्न
Write scientific reasons.
When we drop a feather and a stone at the same time from a height the stone reach the earth faster than a feather.
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उत्तर
- When we drop a feather and a heavy stone at the same time from a height, the feather experiences a buoyant force and a frictional force due to air and therefore floats and reaches the ground slowly.
- But the buoyant and frictional forces on the stone are much less than the weight of the stone and does not affect the speed of the stone much.
- Hence, when we drop a feather and a stone at the same time from a height, the stone reach the earth faster than a feather.
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संबंधित प्रश्न
Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?
What is the acceleration of free fall?
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.
A ball thrown up vertically returns to the thrower after 6 s. Find
- the velocity with which it was thrown up,
- the maximum height it reaches, and
- its position after 4 s.
What force is responsible for the earth revolving round the sun ?
Fill in the following blank with suitable word :
The acceleration due to gravity on the moon is about ………………of that on the earth.
What is the force of gravity on a body of mass 150 kg lying on the surface of the earth? (Mass of earth = 6 x 1024 kg; Radius of earth = 6.4 x 106 m; G = 6.7 x 10-11 Nm2/kg2)
Why does a sharp knife cut objects more effectively than a blunt knife ?
Name the force which stops you falling through the floor.
A metal ball of mass 5 kg falls from a height of 490 m. How much time it will take to reach the ground? (g = 9.8 m/s2)
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The value of acceleration due to gravity of earth :
A force of 15 N acts on a body of mass 2 kg. Calculate the acceleration produced.
How is the acccelaration due to gravity on the surface of the earth realted to its mass and radius ?
In vacuum, all freely falling objects have the same force. Is it true?
What do you understand by the free fall?
The free fall of an object is possible only in ______.
Read the given passage carefully and answer the questions.
| We know that the force of gravity due to the earth acts on each and every object. When we were holding the stone in our hand, the stone was experiencing this force, but it was balanced by a force that we were applying on it in the opposite direction. As a result, the stone remained at rest. Once we release the stone from our hands, the only force that acts on it is the gravitational force of the earth and the stone falls down under its influence. Whenever an object moves under the influence of the force of gravity alone, it is said to be falling freely. Thus the released stone is in a free fall. In free fall, the initial velocity of the object is zero and goes on increasing due to the acceleration due to the gravity of the earth. During free fall, the frictional force due to air opposes the motion of the object and a buoyant force also acts on the object. Thus, true free fall is possible only in a vacuum. |
- Complete the following statement by choosing the right option.
The stone held in the hand is stable because on it ......- two unbalanced forces are exerted.
- only the gravitational force of the earth is exerted.
- gravitational force of the earth is not exerted.
- two balanced forces are exerted.
- Why does free fall not happen on the earth?
- Why does the velocity of the object increase during the free fall?
- Which type of force exerts on the object during free fall?
- Why does free fall happen only in a vacuum?
When is free fall possible?
