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प्रश्न
Explain, why submarines are able to dive underwater as well as a sail on the surface of the water?
उत्तर
Submarines are provided with ballast tanks. When required to dive, the water is allowed to enter the tanks. And when required to sail, the water is forced out by compressed air.
Work is a scalar quantity.
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संबंधित प्रश्न
In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east, as shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero.
A boy throws a rubber ball vertically upwards. What type of work, positive or negative, is done : by the force applied by the boy?
(a) by the force applied by the boy?
(b) by the gravitational force of earth?
How much work is done when a force of 2 N moves a body through a distance of 10 cm in the direction of force?
Ravi applied a force of 10 N and moved a book 30 cm in the direction of the force. How much was the work done by Ravi?
Is the motion of moon around the earth in circular path an accelerated motion?
Can every force produce work?
An electric motor drives a machine which lifts a mass of 4 kg through a height of 10 m in 5 s at a constant speed. Assuming g = 10 ms-2, calculate
(i) the amount of work done, (ii) the power of the machine.
A boy pulls a box up to 10 m with a force of 5 kgf. Calculate the work done by him.
Define energy and state the unit of energy and the law of conservation of energy.
State the energy changes which take place when Water stored in the dam is used to turn turbine in dynamo.
What do you understand by the term energy? Is energy a scalar or vector? How is the energy possessed by a body measured?
An electric motor of power 100 W is used to drive the stirrer in a water bath. If 50% of the energy supplied to the motor is spent in stirring the water. Calculate the work done on the water in one minute.
A bucketful of water is to be drawn from a well ______ will be done when a ______ is applied to do this because there will be a ______ of water.
(displacement, work, force)
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A wind-mill is lifting water from a well.
A man squatting on the ground gets straight up and stand. The force of reaction of ground on the man during the process is ______.
