Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

The modulation frequency of an AM radio station is 250 kHz, which is 10% of the carrier wave. If another AM station approaches you for license what broadcast frequency will you allot ?

  1. 2250 kHz

  2. 2900 kHz

  3. 2750 kHz

  4. 2000 kHz
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As calculated previously, the carrier frequency is 2500 kHz. The next available channel for an AM station would be 2500 kHz + 250 kHz = 2750 kHz.

Multiple choice physics types of energy law of conservation of energy the law of conservation of energy work, energy and machines

The law of conservation of energy implies that the:

  1. Total mechanical energy is conserved

  2. Total kinetic energy is conserved

  3. Total potential energy is conserved

  4. Sum of all kinds of energies is conserved
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Law of conservation of energy implies that energy can neither be created nor destroyed, but can merely be transfered from one form to other. These forms are varied. Thus, when considering all forms of energy,(including workdone) the total sum never changes.

Multiple choice physics types of energy law of conservation of energy the law of conservation of energy work, energy and machines

Energy conservation law says that:

  1. Energy can't be destroyed but can be produced.

  2. Neither energy can be produced nor can be destroyed.

  3. Energy can't be produced but can be destroyed.

  4. Energy can be produced and can be destoyed
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In physics, the law of conservation of energy states that the total energy of an isolated system remains constant—it is said to be conserved over time. Energy can neither be created nor destroyed; rather, it transforms from one form to another.

Multiple choice physics types of energy law of conservation of energy the law of conservation of energy work, energy and machines

The speed of a car of mass 1000 kg is reduced from 20 m/s to 10 m/s. What is the work done by the brakes of the car?

  1. 150 kJ

  2. 120 kJ

  3. 100 kJ

  4. 80 k J
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Work done by the brakes of a car will be the net change in the kinetic energy of car
$W=\dfrac{1}{2}m({v _2}^2-{v _1}^2)$
$W=\dfrac{1}{2}m({10}^2-{20}^2)$
$W=\dfrac{1}{2}m(100-400)$$=$$\frac{1}{2}1000(-300)$
$W=-150000J=-150KJ$
Hence, option A is correct.

Multiple choice physics types of energy law of conservation of energy the law of conservation of energy work, energy and machines

When a stone falls freely towards the earth, its total energy ?

  1. First decreases and then becomes zero

  2. Remains constant

  3. Increases

  4. Decreases
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Since the ball is in free-fall, the only force acting on it is gravity. Therefore, we can use the principle of conservation of mechanical energy - initially the ball has potential energy and no kinetic energy. As it falls, its total energy (the sum of the KE and the PE) remains constant and equal to its initial PE.
Hence, option B is correct.

Multiple choice physics types of energy law of conservation of energy the law of conservation of energy work, energy and machines

When an object falls freely towards the earth, then its total energy :

  1. Increases

  2. Decreases

  3. Remains constant

  4. Can't say
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Since the ball is in free-fall, the only force acting on it is gravity. Therefore, we can use the principle of conservation of mechanical energy - initially the ball has potential energy and no kinetic energy.
As it falls, its total energy (the sum of the KE and the PE) remains constant and equal to its initial PE.
Hence, option C is correct.

Multiple choice physics types of energy law of conservation of energy the law of conservation of energy work, energy and machines

According to law of conservation of energy :

  1. Energy can be created but not destroyed and it can be transformed from one form into another

  2. Energy exists in only one form

  3. Energy exists in many forms but it cannot be transformed

  4. Energy can neither be created nor be destroyed but can change into different forms
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The law of conservation of energy states that in a closed system the total amount of energy is conserved and does not change. This means that energy may change from one form to another, but that the total amount of energy in the closed system remains constant. 

So accoding to this statement it is clear that only option D is best possible.

Multiple choice physics types of energy law of conservation of energy the law of conservation of energy work, energy and machines

What is law of conservation of energy?

  1. Energy can neither be created nor destroyed. It can only be transformed from one to another.

  2. Energy can only be created nor destroyed. It can only be transformed from one to another.

  3. Energy can neither be created but can be destroyed. It can only be transformed from one to another.

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Energy can neither be created nor destroyed. It can only be transformed from one to another is the law of conservation of energy. For example , object falling from certain height converts its potential energy to kinetic energy and at all instant total mechanical energy remains constant.