Tag: physics

Questions Related to physics

Fill in the blank space by choosing the correct word. 
Coal and petroleum are commonly called .................... fuels.

physics sources of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. $renewable$

  2. $biomass$

  3. $fossil$

  4. $tidal$

Show answer
Correct Option: C
Explanation:

Coal and petroleum are commonly called fossil fuels.
Fuels such as coal, oil and natural gas were formed over millions of years from organic matter like plankton, plants and other life forms. Over time, sand, sediment and rock buried the organic matter and it eventually formed large quantities of fuels. These underground resources, known as fossil fuels, are still the primary fuel source for electricity, heating and powering vehicles around the globe.
There are three major forms of fossil fuels: coal, oil and natural gas. All three were formed many hundreds of millions of years ago hence the name fossil fuels. The age they were formed is called the Carboniferous Period. It was part of the Paleozoic Era. "Carboniferous" gets its name from carbon, the basic element in coal and other fossil fuels.

The kind of energy present in fossil fuels is :

physics sources of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. chemical energy

  2. heat energy

  3. potential energy

  4. mechanical energy

Show answer
Correct Option: A
Explanation:

Fossil fuels are mainly comprised of hydrocarbons. Energy is trapped in the form of chemical energy. When fossil fuels are burnt, chemical energy is converted into heat energy.

Coal is a renewable source of energy.

physics sources of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient

Show answer
Correct Option: B
Explanation:

Coal is a fossil fuel. Once it is burnt, it turns to ashes and can never be used again.

State whether given statement is True or False
In hydroelectric plants, the kinetic energy of flowing water drives the generator. 

physics sources of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy production of electricity from solar energy

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Hydroelectric energy, also referred to as hydroelectricity or hydropower, is the use of moving water to produce electricity. This power is generated by converting the kinetic energy of flowing water into mechanical and then electrical energy. This process involves the use of turbines, which consist of a set of blades. The moving water flows over the blades, causing them to turn. The blades are connected to a rotating drive shaft. The mechanical energy of the drive shaft is transferred to a generator through a gearbox. The generator uses the mechanical energy of the drive shaft to move an electric conductor (typically coils of copper wire) through a magnetic field, which causes electrons to flow through the conductor, generating electricity. The electricity is then fed into the electrical grid to be used in homes, businesses, and by industry.
Hence, the statement is true.

A body is falling freely under the action of gravity alone in vacuum. Which of the following quantities remain constant during the fall?

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. Kinetic energy

  2. Potential energy

  3. Total mechanical energy

  4. Total linear momentum

Show answer
Correct Option: C
Explanation:
As the body is falling freely under gravity, the potential energy decreases continuously and kinetic energy increases continuously as all the conservative forces are doing work. So, total mechanical energy $(PE + KE)$ of the body will be constant.
At point A total mechanical energy will be $EA = K.E + P.E$
$E _{A}=\dfrac{1}{2}mv^{2}+m _{g}H$
As velocity will be zero at $A$, so its kinetic energy will be zero 
$E _{A}=M _{g}H$
Velocity at point $B$ will be 
$V _{B}=\sqrt{2gh}$
So energy at point $B$ will be 
$E _{B}=KE+PE$
$E _{B}=\dfrac{1}{2}m(2gh)+mg(H-h)$
$E _{B}=mgh+mgH-mgh$
$E _{B}=mgH$
Now velocity at point $C$ will be 
$V _{C}=\sqrt{2gh}$
So energy at point $C$ will be
$ E _{C}=KE+PE$
$E _{C}=\dfrac{1}{2}m(2gH)+mg(0)$
So, total mechanical energy will remain same (if we neglect the air friction).

While falling

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. Potential energy

  2. Kinetic energy

  3. Both A & B

  4. None

Show answer
Correct Option: C
Explanation:

While it is falling it has certain velocity,as kinetic energy is defined as the virtue of its state of motion it will have kinetic energy.As it is at certain height it will have Potential energy which is defined by virtue of state of its position.Hence ball has both potential and kinetic energy.

A body rolling down a hill has

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. K.E. only

  2. P.E. only

  3. Neither K.E. nor P.E

  4. Both (a) and (b)

Show answer
Correct Option: D
Explanation:

While rolling down from hill a body will have some Potential energy due to height wrt to ground and due to rolling it will have some Kinetic energy .As it will keep rolling down , Its PE will change into KE

So $E _{Total}=mgh+\dfrac{mv^2}{2}$

A flying aeroplane has:

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. only potential energy

  2. only kinetic energy

  3. both potential and kinetic energy

  4. none of these

Show answer
Correct Option: C
Explanation:

An flying aeroplane required some work to be done against gravity to go upto that much height that work will be stored as potential energy of the body. Also aeroplane has some mass and moving with some velocity so has some kinetic energy also. 

So this poses both potential as well as kinetic energy.

A body rolling down a hill has:

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. K.E. only

  2. P.E. onley

  3. neither K.E. and P.E.

  4. both K.E and P.E

Show answer
Correct Option: D
Explanation:

Taking toe of the hill as refrence point so some work against the gravity is done to raise the body to top of the hill so it poses some potential energy equal to mgh where m is mass and g is acceleration due to gravity and h is vertical height.

Also he is moving so he must have some kinetic energy.
So body rolling along the hill have both kinetic as well as potential energy.

Which of the following has both kinetic energy and potential energy ?

physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

  1. A flying bird

  2. A bent bow about to shoot an arrow

  3. An athlete running at full speed

  4. None of the above

Show answer
Correct Option: A
Explanation:

Since the bird is flying is must be at some distance from the ground and Potential energy is present when there is some height associated with that object (Since P.E = mgh). Also  the bird has mass and thus gravity will be acted on it. Kinetic energy is present for an object if it has velocity.This a flying bird has both kinetic energy and potential energy.