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प्रश्न
Why does a sharp knife cut objects more effectively than a blunt knife ?
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उत्तर
The area under the sharp knife is less than the area under the blunt knife. Hence, the pressure exerted by the sharp knife is more than the pressure exerted by the blunt knife on an object. Therefore, when a same amount of force is applied on both the knives, the sharp knife penetrates deeper into the object than the blunt knife.
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संबंधित प्रश्न
A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground.
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.
When an object is dropped from a height, it accelerates and falls down. Name the force which accelerates the object.
During a free fall, will heavier objects accelerate more than lighter ones ?
What is the usual value of the acceleration due to gravity of earth ?
The acceleration produced in a body by a force of given magnitude depends on
How is the acccelaration due to gravity on the surface of the earth realted to its mass and radius ?
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.
The value of gravitational acceleration at the centre of earth is zero.
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?
