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प्रश्न
Right or wrong sentence:
The value of gravitational acceleration at the centre of earth is zero.
पर्याय
Right
Wrong
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उत्तर
The given sentence is right.
Explanation:
Gravity is a vector. By symmetry (Newton’s shell theorem) the gravitational pull of all mass elements around the centre cancels at the centre, so the net gravitational acceleration there is zero. For a uniform spherical Earth, one finds `M(r) ∝ r^3 so g(r)`
= `G·M(r)/r^2 ∝ r`
Hence, g(0) = 0
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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?
A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate
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What is the acceleration produced in a freely falling body of mass 10 kg ? (Neglect air resistance)
When an object is dropped from a height, it accelerates and falls down. Name the force which accelerates the object.
What force is responsible for the earth revolving round the sun ?
During a free fall, will heavier objects accelerate more than lighter ones ?
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.
What would be the value of ‘g’ on the surface of the earth if its mass was twice and its radius half of what it is now?
A force of 15 N acts on a body of mass 2 kg. Calculate the acceleration produced.
A force acts for 10 s on a stationary body of mass 100 kg, after which the force ceases to act. The body moves through a distance of 100 m in the next 5 s. Calculate : The acceleration produced by the force
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?
A force acts for 0.1 s on a body of mass 2.0 kg initially at rest. The force is then withdrawn and the body moves with a velocity of 2 m s-1. Find the magnitude of the force.
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.
What force, in newton, your muscles need to apply to hold a mass of 5 kg in your hand? State the assumption.
Explain why:
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The free fall of an object is possible only in ______.
Write scientific reasons.
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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. |
- 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?
