Energy Test - 6

According to the question the correct option will be ‘B’ because Energy is defined as the capacity to do work.

According to the question the correct option will be ‘B’ because the kilowatt hour is a unit of energy equal to 1,000 watt-hours, or 3.6 mega joule. If the energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt-hours is the product of the power in kilowatts and the time in hours.

1 kilowatt hour =1000 × 3600joule = 3.6 × 10⁶ J

According to the question the correct option will be ‘D’ because Force is represented as [MLT⁻²] and length [L]

Energy f × d is [MLT⁻²] × [L] = [ML²T⁻²]

if Force and length are quadrupled in value Energy

4[MLT⁻²] × 4[L] = 16 [ML²T⁻²]

Unit increased by 16 times.

According to the question the correct option will be ‘C’ because Electron volt or eV is the unit of energy (electrical energy).

1 eV = 1.6 × 10⁻¹⁹ coulombs (charge of an electron) × 1 volt.

According to the question the correct option will be ‘B’ because It is a fact that

1 calorie = 4.184 J 

According to the question the correct option will be ‘B’ because If a body is at rest then its position does not changes if position is not changing then $\frac{dx}{dt}$ = 0 so velocity is zero.

If Instantanious velocity is zero then speed is also zero this means if speed is zero then kinetic energy is also zero.

If v=0 then mv=0 i.e. momentum is also zero.

But a body raised upto some height against gravity and is at rest but it poses some potential energy which when released will be converted to kinetic energy.

So a body at rest can poses only potential energy from all these options.

According to the question the correct option will be ‘B’ because when the man moves on a horizontal surface, then work done by gravity is zero since gravitational force acts perpendicular to the displacement.

And the normal force will be also perpendicular to displacement so work done by It also is zero. - - - - - - - - 1

But frictional force is acting opposite to displacement so work done by frictional force is negative. - - - - - - - - - - - 2

Using statement (1) and (2) we can say that work done by contact force is non – zero.

According to the question the correct option will be ‘C’ because Potential energy is energy stored in an object. This energy has the potential to do work. Gravity gives potential energy to an object. This potential energy is a result of gravity pulling downwards. The gravitational constant, g, is the acceleration of an object due to gravity. This acceleration is about 10 meters per second on earth. The formula for potential energy due to gravity is PE = mgh. As the object gets closer to the ground, its potential energy decreases while its kinetic energy increases.

In this case, a body of mass 5 kg kept at a height of 10 m. So the potential energy is given as 5 * 10 × 10 = 500 J.

Hence, the potential energy of a body of mass 5 kg kept at a height of 10 m is 500 J.

According to the question the correct option will be ‘C’ because Energy is produced in a star's center, where pressures are enormous and temperatures reach 27 million (15 million). This causes nuclear fusion—atoms of hydrogen are ripped apart and fuse (join) to form helium. These reactions release vast amounts of energy, which makes the star shine.

According to the question the correct option will be ‘B’ because Any work done on a body changes in is potential energy, as we deduce from work energy theorem.

\(\mathrm{W}_{\mathrm{T}}=\Delta \mathrm{K} . \mathrm{E}\)

According to the question the correct option will be ‘C’ because Total energy = Potential Energy + Kinetic Energy = 800 J

At certain height when Potential Energy = Kinetic Energy = 400 J

Kinetic Energy  =$\frac{1}{2}$ mv² = 400

⇒v=20 m/s

According to the question the correct option will be ‘B’ because S.I. unit of energy is N−m which is also known as joule and CGS unit of energy is Dyne−cm which is also known as erg.

and 1erg = 10⁻⁷J

So answer to the question is B.

According to the question the correct option will be ‘C’ because kilowatt is the unit of power.

Joule is the unit of energy (capacity to do work).

Newton- meter is the unit of work.

Kilowatt hour is the commercial unit of energy.

Hence the correct answer is option C.

The given unit \(k g m^{2} s^{-2}\) is unit of energy and any of the energy either potential or kinetic will have same unit

also work done is given by \(F . S\) or \(\mathrm{kgms}^{-2} . \mathrm{m}\) or \(\mathrm{kgm}^{2} \mathrm{s}^{-2}\)

so the unit of work is also same.

so the given unit represent unit for all the three quantities in the options.

Energy is defined as the ability to do work and its SI unit is Joule.

Energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object. Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed. 

Hence, the correct option is (C).