The unit of power SI (watt) is equivalent to:
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Power = work/time, so its dimensions are kg m² s⁻³.
One mega watt-hour is equal to:
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1 MW = 10⁶ W and 1 hour = 3600 s.
Work done under a force is negative if the force and displacement are:
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W = Fd cos θ; for opposite directions θ = 180° and work is negative.
A body of mass 3 kg lies on the surface of the table 2 m high. It is moved on the surface by 4 m. The change of P.E will be:
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The height does not change, so gravitational potential energy does not change.
The work needed to lift a body of mass 'm' from the surface of earth to an infinite distance is:
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The required work to move a mass to infinity equals the magnitude of its gravitational potential energy at the surface.
One erg is equal to:
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The escape velocity of a body depends upon:
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Escape velocity depends on the mass and radius of the planet, not the mass of the escaping body.
The consumption of energy by a 60-watt bulb in 2 sec is:
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Water from a stream is falling on the blades of a turbine at the rate of 100 kg/s. If the height of the stream is 100 m then the power delivered to the turbine is:
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Power = mass flow rate × g × height; using g ≈ 10 m/s² gives 100 kW.
The source of geothermal energy is:
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Geothermal energy is largely associated with heat from Earth's interior, including radioactive decay.
The momentum of particle is numerically equal to its kinetic energy. What is the velocity of the particle?
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A body moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joules, the angle which the force takes with the direction of motion of the body is:
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Use W = Fd cos θ: 25 = 5×10×cos θ.
Solar cells are made up from the material called:
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Silicon is the common semiconductor material used in solar cells.
The P.E of an object on the surface of earth is equal to:
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Taking gravitational potential energy to be zero at Earth's surface/reference level in this question.
If moon’s radius is 1600 km and 'g' on its surface is 1.6 m/s², then the escape velocity on the moon is:
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Use vₑ = √(2gr), with r = 1.6×10⁶ m.
When a body is lifted through a height 'h', the work done on the body appears in the form of:
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Lifting a body increases its gravitational potential energy.
Which one is the biggest unit of energy?
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A kilowatt-hour equals 3.6×10⁶ joules.
A body of mass 2 kg is thrown vertically with a kinetic energy of 490 J. If g = 9.8 m/s², the height at which the kinetic energy becomes half its original value is:
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Half the initial kinetic energy has been converted into potential energy.
How much water a pump of 2 kW can raise in one minute to a height of 10 m, take g=10 ms⁻²?
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Use P = mgh/t and take 1 kg of water ≈ 1 liter.
In a power of 1 kW is maintained for 1 second, the work done is equal to:
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Work = power × time = 1000 W × 1 s.
