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प्रश्न
What do you understand by the term energy? Is energy a scalar or vector? How is the energy possessed by a body measured?
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उत्तर
Energy is defined as the capacity of a body to do work. Energy is a scalar quantity. The energy possessed by a body is measured by the amount of work done by a body while changing its state of rest or state of motion.
संबंधित प्रश्न
Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?
In which of the following cases, is work being done?
(i) A man pushing a wall.
(ii) a coolie standing with a load of 12 kgf on his head.
(iii) A boy climbing up a staircase.
1 J = ______ calorie.
A boy of weight 40 kgf climbs up the 15 steps, each 15 cm high in 10 s and a girl of weight 20 kgf does the same in 5 s. Compare:
- the work done, and
- the power developed by them. Take g = 10 N kg-1.
A water pump raises 50 litres of water through a height of 25 m in 5 s. Calculate the power of the pump required.
(Take g = 10 N kg-1 and density of water = 1000 kg m-3)
In case of negative work, the angle between the force and displacement is :
Give an example
Electrical energy changes to heat energy.
State larger units of power.
A girl of mass 40 kg runs a height of 80 stairs, each 25 cm high with a load of 20 kg on her head in 25 sec. If g is 10 m/s2, find:
(i) Gravitational force acting on the girl.
(ii) Work done by her.
(iii) Useful work done by her.
(iv) Her power in watt.
