Work and Energy Test

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Work and Energy Test - 20

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Weekly Quiz Competition

Question 1
1 / -0

The practical unit for the measurement of electric power is:

A
watt

B
kilowatt

C
kilowatt hour

D
horse power
Solution
- SI unit of power is $$J/s \ (watt).$$
- Watt can be represented as $$kilowatt \ (10^3$$watt).
- Kilowatt hour is unit of energy (or watt sec, Kilowatt can be changed to watt and hour to sec) so this is unit of energy.
- Horsepower is similarly another unit of power. But it is not very convenient to use since we are using the SI units of energy (joules) and time (seconds) to calculate power. We will have to divide the result by $$746$$ to obtain power in Horsepower. $$(\because 1 \ HP=746 \ W)$$
So, the best possible answer is watt, i.e. option A.
Question 2
1 / -0

An agent does $$4$$ J of work in $$2$$ s. Find the power of the agent.

A
$$1$$ W

B
$$3$$ W

C
$$2$$ W

D
$$6$$ W

Solution

Given: Work done $$W=4\ J$$, time $$t=2\ s$$
We know that $$Power=\dfrac{Work}{Time}=\dfrac{4}{2}=2\ W$$
Question 3
1 / -0

Which of the following will lead to a change in kinetic energy of a body?

A
change in its mass

B
change in its velocity

C
all of the above

D
none of the above

Solution

Kinetic energy of the body $$K = \dfrac{1}{2}mv^2$$
$$\implies$$ $$K \propto m$$ and $$K \propto v^2$$
Thus changing either the mass of the body or its velocity will lead to a change in kinetic energy of a body.
Question 4
1 / -0

What is potential energy?

A
Energy of an object due to its position or arrangement in a system

B
Energy of an object due to its nature or arrangement in a system

C
Energy of an object due to its shape or arrangement in a system

D
None

Solution

The potential energy is the stored energy of an object due to its position.
some examples of potential energies are gravitational potential energy, Electrostatic potential energy and elastic energy etc.
A body placed at ground will have less gravitational potential energy than a body placed at some height. therefore, potential energy changes by changing the position of object. Hence, Option A is correct.
Question 5
1 / -0

Which of the following is NOT a correct unit for work?

A
erg

B
watt

C
joule

D
Nm

Solution

Option A
erg- It is the unit of work in CGS system

Option B-
Watt- It is the unit of power which work per unit time

Option C-
joule- It is the unit of work in MKS system in terms of energy

Option D-
Nm- Newton meter is the unit of work in terms of force and displacement.
Question 6
1 / -0

Unit of work is

A
Joule

B
Newton

C
Tesla

D
None of these

Solution

Work is defined as the product of force applied and the displacement of the object multiplied by the $$cos$$ of angle between the force applied and the displacement.
Work done $$W = F s \cos\theta$$

SI unit of work is Joule $$(J)$$.
Question 7
1 / -0

If Rahul has done the same amount work in less time compared to Rohan then:

A
Rahul has more power

B
Rohan has more power

C
Both Rahul and Rohan have equal power

D
Rahul has more energy than Rohan

Solution

The relation between power P and work W is given by $$P=W/t$$, where, $$t$$ be the time
For same amount of doing work, Power $$P\propto \dfrac 1t$$
$$\because$$ Rahul is taking less time in compare to Rohan so, Rahul has more power.
Option A
Question 8
1 / -0

SI unit of electrical energy is

A
Joule

B
Kilowatt hour

C
KiloJoule

D
Watt hour

Solution

SI unit of electrical energy is Joule.
$$1 Joule = 1 Volt \times 1 ampere \times 1 second$$
Question 9
1 / -0

What is kinetic energy?

A
Energy possessed by a body by the virtue of its motion

B
Energy possessed by a body by the virtue of its shape

C
Energy possessed by a body by the virtue of its size

D
None

Solution

Correct Option: A
Explanation: The energy which a body possesses by virtue of being in motion is called as kinetic energy. If we want to stop a moving body then we must do some work on the body to stop it which means that a moving body possesses energy because of motion.
If an object of mass $$m$$ moving with the velocity $$v$$, The kinetic energy is defined as,
$$K.E. = \dfrac{1}{2}mv^2$$
Hence, Option A is correct.
Question 10
1 / -0

A body at rest can't have

A
Momentum

B
Kinetic energy

C
Both $$a$$ & $$b$$

D
None

Solution

Given, A body is in rest, its mean that $$v=0$$
Momentum $$P=mv=m\times 0=0$$
Kinetic energy $$K.E=\dfrac12 mv^2=\dfrac12m\times 0^2=0$$
Hence, Momentum and Kinetic energy of body will be zero when it is in rest.

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Re-Attempt Weekly Quiz Competition

Work and Energy Test - 20

Result

Work and Energy Test - 20

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Rank

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SHARING IS CARING

Question 1

watt

kilowatt

kilowatt hour

horse power

Solution

Question 2

$$1$$ W

$$3$$ W

$$2$$ W

$$6$$ W

Solution

Question 3

change in its mass

change in its velocity

all of the above

none of the above

Solution

Question 4

Energy of an object due to its position or arrangement in a system

Energy of an object due to its nature or arrangement in a system

Energy of an object due to its shape or arrangement in a system

None

Solution

Question 5

erg

watt

joule

Nm

Solution

Question 6

Joule

Newton

Tesla

None of these

Solution

Question 7

Rahul has more power

Rohan has more power

Both Rahul and Rohan have equal power

Rahul has more energy than Rohan

Solution

Question 8

Joule

Kilowatt hour

KiloJoule

Watt hour

Solution

Question 9

Energy possessed by a body by the virtue of its motion

Energy possessed by a body by the virtue of its shape

Energy possessed by a body by the virtue of its size

None

Solution

Question 10

Momentum

Kinetic energy

Both $$a$$ & $$b$$

None

Solution

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