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प्रश्न
Write a short note.
Free Fall
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उत्तर
- The motion of any object under the influence of the force of gravity alone is called free fall.
- In free fall, the initial velocity of the object is zero, and it goes on increasing due to the acceleration due to 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.
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संबंधित प्रश्न
A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate
- the maximum height to which it rises.
- the total time it takes to return to the surface of the earth.
When an object is dropped from a height, it accelerates and falls down. Name the force which accelerates the object.
State whether the following statement is true or false :
A falling stone also attracts the earth.
What do you mean by the term free fall ?
Explain why, the tip of a sewing needle is sharp.
Name the force which wears away two surfaces as they move over one another.
Name the force which pulled the apple off Isaac Newton’s tree.
An object thrown vertically upwards reaches a height of 500 m. What was its initial velocity? How long will the object take to come back to the earth? Assume g = 10 m/s2.
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)
The acceleration produced in a body by a force of given magnitude depends on
A force of 10 N acts on a body of mass 5 kg. Find the acceleration produced.
A force causes an acceleration of 10 m s-2 in a body of mass 500 g. What acceleration will be caused by the same force in a body of mass 5 kg?
Define the term acceleration due to gravity? Write its S.I. unit.
A body falls freely under gravity from rest and reaches the ground in time t. Write the expression for the height fallen by the body.
Right or wrong sentence:
The value of gravitational acceleration at the centre of earth is zero.
Define acceleration due to gravity.
Distinguish between:
Universal gravitational constant – Gravitational acceleration of earth.
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?
