Work and Energy Test

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Work and Energy Test - 38

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Weekly Quiz Competition

Question 1
1 / -0

The amount of work done (or, energy spent) by a source of power $$1kW$$ in $$1h$$ time is:

A
$$1J$$

B
$$1Wh$$

C
$$1kWh$$

D
$$1calorie$$

Solution

$$Energy$$ $$spent$$ = $$Power \times time$$
$$E=1kWh \times 1h$$ = $$1kWh$$
$$1kWh$$ is the amount of work done (or, energy spent) by a source of $$1kW$$power in $$1h$$ time.
Question 2
1 / -0

The S.I. unit of energy is

A
erg

B
calorie

C
Joule

D
None of these

Solution

Energy is capacity of doing work. The unit of energy is same as that of work. So, S.I. unit of energy is $$joule(J)$$.
Question 3
1 / -0

A fruit hanging from the top branch of a tree possesses

A
gravitational potential energy

B
elastic potential energy

C
kinetic energy

D
sound energy

Solution

A fruit, hanging from the top branch of a tree, is at rest at a certain height from the earth"s surface.
So, it possesses gravitational potential energy.
Question 4
1 / -0

Which of the following is an example of zero work even when the body suffers a displacement from its initial position?

A
A coolie carrying a load on his head and moving forward on a horizontal road

B
A fielder catching a ball

C
A child pushes a wall

D
A child pulling a toy car

Solution

When a coolie carries a load on his head, he applies a force upwards against the weight of the load, i.e., against the gravitational force. And the displacement is forward horizontally. So, the angle between the force and the displacement is $${90}^{\circ}$$ and the work done is zero.
To catch a ball, work done is negative as the ball moves in the opposite direction of force before coming to rest.
A child pushing a wall is an example of zero work as the wall suffers zero displacements.
A child pulling a toy car is an example of positive work.
Question 5
1 / -0

A crane pulls up a car of mass $$500kg$$ to a vertical height of $$4m$$. So, work done by the crane is:

A
$$19.6J$$

B
$$19.6kJ$$

C
$$19600kJ$$

D
$$4900J$$

Solution

To raise the car, the crane has to do work against the force of gravity.
Therefore, the force required to lift the car, $$F=mg=500\times{9.8}N=4900N$$
Displacement, $$S=$$ vertical height raised $$=4m$$.
$$\therefore$$ Work done, $$W=F.S=4900\times{4}J=19600J=19.6kJ$$
Question 6
1 / -0

Watt hour represents:

A
Electric energy

B
Current

C
Voltage

D
Power

Solution

The watt-hour (Wh) is a unit of electric energy equivalent to one watt (1 W) of power expended for one hour (1 h) of time. Watt-hour is commonly used in electrical applications.
$$1\ Wh = 1\times 60\times 60 = 3600\ J$$
Question 7
1 / -0

Unit used in selling electrical energy to consumer is:

A
$$Volt-Ampere$$

B
$$Kilowatt-hour$$

C
$$Volt/second$$

D
None of these

Solution

The commercial unit of electrical energy is $$Kilowatt-hour\ (kWh)$$.
$$1\ kWh$$ is equal to $$1\ unit$$ of energy.
Question 8
1 / -0

Calculate the power of a source if it produces energy of $$250\ J$$ in $$10\ s$$.

A
$$2500\ W$$

B
$$2.5\ W$$

C
$$25\ W$$

D
Zero

Solution

Given,
Energy, $$E = 250\ J$$
Time, $$t = 10$$ s

We know,
Power of the source, $$P = \dfrac{E}{t}$$

$$P = \dfrac{250}{10}$$

$$P = 25\ W$$
Question 9
1 / -0

Convert 1 kWh to SI unit of energy.

A
$$3.6\times 10^6J$$

B
$$3.6\times 10^8J$$

C
$$1.8\times 10^6J$$

D
$$1.8\times 10^8J$$

Solution

We know that,
$$1\ watt = 1\ joule/sec$$ and $$1\ kW=1000\ watt$$
Therefore,
$$1\ kWh$$ $$ = 1000\ watt\times 1\ hour = 1000\ joule/sec \times 3600\ sec$$ $$ = 3.6\times 10^6$$ $$J$$
Question 10
1 / -0

Energy consumed in our house has a unit of

A
watts

B
horse power

C
kilowatt-hours

D
none

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Re-Attempt Weekly Quiz Competition

Work and Energy Test - 38

Result

Work and Energy Test - 38

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SHARING IS CARING

Question 1

$$1J$$

$$1Wh$$

$$1kWh$$

$$1calorie$$

Solution

Question 2

erg

calorie

Joule

None of these

Solution

Question 3

gravitational potential energy

elastic potential energy

kinetic energy

sound energy

Solution

Question 4

A coolie carrying a load on his head and moving forward on a horizontal road

A fielder catching a ball

A child pushes a wall

A child pulling a toy car

Solution

Question 5

$$19.6J$$

$$19.6kJ$$

$$19600kJ$$

$$4900J$$

Solution

Question 6

Electric energy

Current

Voltage

Power

Solution

Question 7

$$Volt-Ampere$$

$$Kilowatt-hour$$

$$Volt/second$$

None of these

Solution

Question 8

$$2500\ W$$

$$2.5\ W$$

$$25\ W$$

Zero

Solution

Question 9

$$3.6\times 10^6J$$

$$3.6\times 10^8J$$

$$1.8\times 10^6J$$

$$1.8\times 10^8J$$

Solution

Question 10

watts

horse power

kilowatt-hours

none

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