Work and Energy Test

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Work and Energy Test - 18

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Weekly Quiz Competition

Question 1
1 / -0

Work is said to be done when:

A
(i) a force should act on an object, and (ii) the object must be displaced.

B
(i) no force should act on an object, and (ii) the object must be displaced.

C
(i) a force should act on an object, and (ii) the object must not be displaced.

D
(i) no force should act on an object, and (ii) the object must not be displaced.

Solution

Work is done whenever the given condition is satisfied:
(i) A force should act on an object
(ii) There is a displacement of the body caused by the applied force along the direction of the applied force.
Question 2
1 / -0

The expression for work done, when the displacement is in the direction of the force is:

A
$$ F \times S$$

B
$$ 0$$

C
$$- \dfrac{F}{ S}$$

D
$$ \dfrac{F \times S}{2}$$

Solution

In this case, the force and the displacement acts along the same direction. So, work done is positive. Therefore, the expression for work done is given as $$Work\ done=Force(F)\times Displacement(S)$$.
Question 3
1 / -0

The CGS unit for energy is:

A
dyne

B
erg

C
centimeter

D
joule

Solution

The CGS unit for energy is erg.
$$1\ erg = 10^{-7} J$$
Question 4
1 / -0

The power output of a motor is $$5 \ kW.$$ What is the work done by the motor in $$5 \ s$$?

A
2.5 k J

B
25 kJ

C
250 k J

D
25000 k J

Solution

Power $$=\dfrac{Work }{Time}$$
So Work $$={Power}\times Time$$
Given:
$$P=5 \ kW$$
$$t= 5 \ sec$$
$$W=5\times 5 =25 \ kJ$$

Hence, option B is correct.
Question 5
1 / -0

The capacity of a body to do work is called ______ .

A
Stamina

B
Potential

C
Velocity

D
Energy

Solution

Energy is the capacity of a physical system to perform work. Energy exists in several forms such as heat energy, kinetic or mechanical energy, light energy, potential energy, electrical energy, or other forms. According to the law of conservation of energy the total energy of a system remains constant, though energy may transform into another form.
The SI unit of energy is the joule (J) or newton-meter (N-m). Joule is also the SI unit of work.
Question 6
1 / -0

The rate of doing work is called ........

A
power

B
energy

C
acceleration

D
velocity

Solution

power is the rate of doing work. It is equivalent to an amount of energy consumed per unit time. In the SI system, the unit of power is the joule per second (J/s).
Question 7
1 / -0

Energy can be defined as:

A
The capacity to do work

B
Work done in unit time

C
A push or a pull

D
Attraction between two oppositely charged particles

Solution

Energy is the capacity of a system to perform work. The various forms of energy include potential energy, kinetic energy, heat energy, chemical energy, electrical energy and light energy.
Question 8
1 / -0

The force needed to produce an acceleration of $$\displaystyle 6\ { m }/{ { s }^{ 2 } }$$ in a ball of mass $$4\ kg$$ will be:

A
$$24\ N$$

B
$$30\ N$$

C
$$32\ N$$

D
$$20\ N$$

Solution

Given,
Mass, $$m=4\ kg$$
Acceleration, $$a=6\ m/s^2$$

We know,
Force, $$F=m\times a$$
$$F=4\times 6$$
$$F=24\ N$$
Question 9
1 / -0

When the time taken to complete a given amount of work increases, then :

A
power generated increases

B
power generated decreases

C
energy increases

D
energy decreases

Solution

Power is the rate of energy generation(or absorption).
The relation between time and power is P = $$\dfrac{E}{t}$$.
So power and time are inversely proportional to each other. Hence when the time to complete a given amount of work increases then the power generated decreases.
Question 10
1 / -0

Which among the following is the commercial unit of electrical energy?

A
Volt

B
Watt

C
Ampere

D
KWh

Solution

Answer is D.

The kilowatt-hour is a unit of energy equal to 1,000 watt-hours, or 3.6 mega-joules. 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. The kilowatt-hour is commonly used as a billing unit for energy delivered to consumers by electric utilities.

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Work and Energy Test - 18

Result

Work and Energy Test - 18

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Question 1

(i) a force should act on an object, and (ii) the object must be displaced.

(i) no force should act on an object, and (ii) the object must be displaced.

(i) a force should act on an object, and (ii) the object must not be displaced.

(i) no force should act on an object, and (ii) the object must not be displaced.

Solution

Question 2

$$ F \times S$$

$$ 0$$

$$- \dfrac{F}{ S}$$

$$ \dfrac{F \times S}{2}$$

Solution

Question 3

dyne

erg

centimeter

joule

Solution

Question 4

2.5 k J

25 kJ

250 k J

25000 k J

Solution

Question 5

Stamina

Potential

Velocity

Energy

Solution

Question 6

power

energy

acceleration

velocity

Solution

Question 7

The capacity to do work

Work done in unit time

A push or a pull

Attraction between two oppositely charged particles

Solution

Question 8

$$24\ N$$

$$30\ N$$

$$32\ N$$

$$20\ N$$

Solution

Question 9

power generated increases

power generated decreases

energy increases

energy decreases

Solution

Question 10

Volt

Watt

Ampere

KWh

Solution

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