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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
A ball thrown up vertically returns to the thrower after 6 s. Find
- the velocity with which it was thrown up,
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Explain why, if a stone held in our hand is released, it falls towards the earth.
What is the usual value of the acceleration due to gravity of earth ?
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(a) Arrange these values of g according to the increasing distances from the surface of the earth (keeping the value of g nearest to the surface of the earth first)
(b) If the value of distance F be 10000 km from the surface of the earth, state whether this distance is deep . inside the earth or high up in the sky. Give reason for your answer.
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If the mass of a planet is eight times the mass of the Earth and its radius is twice the radius of the Earth, what will be the escape velocity for that planet?
A ball falls off a table and reaches the ground in 1 s. Assuming g=10 m/s2, calculate its speed on reaching the ground and the height of the table.
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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.
1) 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.
2) Why does free fall not happen on the earth?
3) Why does the velocity of the object increase during the free fall?
4) Which type of force exerts on the object during free fall?
5) Why does free fall happen only in a vacuum?
