Why does an object float or sink when placed on the surface of water?

Question:

Answer:

Objects of density less then the density of water float on the surface of water whereas of thin objects with a density greater than the density of water sink in water.

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Define average power.

A lamp consumes 1000 J of electrical energy in 10 s. What is its power?

Define 1 watt of power.

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The kinetic energy of an object of mass, m moving with a velocity of 5 ms–1 is 25 J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times?

Write an expression for the kinetic energy of an object.

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Define 1 J of work.

Write an expression for the work done when a force is acting on an object in the direction of its displace-ment.

When do we say that work is done?

The volume of a 500 g sealed packed is 350 cm3 will the packet float or sink in water if the density of water is 1 g cm–3 ? What will be the mass of the water displaced by this packet ?

The volume of 50 g of a substance is 20 cm3. If the density of the water is 1 g cm–3 will the substance float or sink ?

Why does a block of plastic released under water come up to the surface of water ?

In what direction does the buoyant force on an object immersed in a liquid act ?

A ball thrown up vertically returns to the thrower after 6s find. (a) the velocity with which it was thrown up. (b) the maximum height it reaches and (c) it's position after 4s.

A stone is allowed to fall from the top of a tower 100m high and at the same time another stone is projected vertically when and where the two stones will meet.

Calculate the force of gravitation between the earth and the sun, given that the mass of earth = 6 × 1024 kg. and of the sun = 2 × 1030 kg. The average distance between the two is 1.5 × 1011 m.

A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2 find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone ?

A stone is released from the top of a tower of height 19.6 m calculate it's final velocity just before touching the ground.

A ball is thrown vertically upwards with a velocity of 49 m/s Calculate. (i) The maximum height to which it rises. (ii) The total time it takes to return to the surface of the earth.

Gravitational force on the surface of the moon is only 1/6 as strong gravitational force on the earth. What is the weight in newtons of a 10 kg object on the moon and on the earth ?

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Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets his friend at the equator will the friend agree with the weight of gold bought ? If not, why ? [Hint : The value of g is greater at the poles than at the equator]

What do we call the gravitational force between the earth and an object.

What is the acceleration of free fall ?

What is the importance of universal law of gravitation?

What happens to the force between two objects, if (i) The mass of one object is doubled. (ii) The distance between the objects is doubled and tripled. (iii) The masses of both objects are doubled.

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What is the reason for the occurrence of tides in the oceans ?

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Chapter 9 NCERT Class 9 Science SOLUTIONS