Tag: forms of energy and energy conservation

Questions Related to forms of energy and energy conservation

Identify, which of the following energies can be positive only:

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. Kinetic energy

  2. Potential energy

  3. Mechanical energy

  4. Both kinetic and mechanical energies.

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Correct Option: A
Explanation:

Potential energy is the energy stored by the virtue of the position of a body.While,kinetic energy is the energy possessed by the virtue of motion.
Hence, K.E is always +ve .
When a body is raised to a particular height,work is done against the force of gravity and P.E is $ - $ve.
When the body is falling freely the work is done in the direction of force of gravity and P.E is $+$ ve.

Identify, which of the following energies can be positive only

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. kinetic energy

  2. potential energy

  3. mechanical energy

  4. both kinetic and mechanical energies

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Correct Option: A
Explanation:

Only kinetic energy can have positive value. Potential energy has negative value and mechanical energy is combination of these two hence can either be positive or negative.

What kind of energy transformation takes place

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. When an arrow is shot its bow

  2. running water

  3. Moving plane

  4. A stretched spring

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Correct Option: A
Explanation:

The kind of energy transformation takes place

When an arrow is short its bow

A ball is dropped from $30\ m$ on hitting the ground if it loses $40$% of its energy, it rebounds to a height equal to

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. $12\ m$

  2. $15\ m$

  3. $18\ m$

  4. $16\ m$

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Correct Option: A

A small sphere is moving at a constant speed in a vertical circle. Below is a list of quantities that could be used to describe some aspect of the motion of the sphere.
$I$   -kinetic energy
$II$  -gravitational potential energy
$III$  - momentum
Which of these quantities will change as this sphere moves around the circle?

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. $I$ and $II$ only

  2. $I$ and $III$ only

  3. $III$ only

  4. $II$ and $III$ only

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Correct Option: D
Explanation:

Speed is given as constant. Though the velocity is changing only in direction, its magnitude remains the same. Thus the kinetic energy remains constant as it is a scalar quantity but momentum would change as it is a vector quantity.
Also as the elevation of the ball keeps on changing during the motion, the potential energy changes

Energy required to break a bond of DNA is approximately

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. ~ 1 eV

  2. ~ 0.1 eV

  3. ~ 0.01 eV

  4. ~ 2.1 eV

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Correct Option: A
Explanation:

The bond energy of a DNA molecule is 1 eV, so this will be the energy required to break the bond

A system absorbs 600 J of energy and does work equivalent to 400 J of energy. The internal energy change is

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. 1000 J

  2. 200 J

  3. 600 J

  4. 300 J

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Correct Option: B
Explanation:

$\begin{array}{l} We\, \, know\, \, that, \ \Delta E=Q+W \ =600+\left( { -400 } \right)  \ =200J \end{array}$

Hence,
Option $B$ is correct.

On a microscopic scale, all forms of energy may be studied as

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. potential

  2. kinetic

  3. potential or kinetic

  4. nuclear

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Correct Option: C
Explanation:

On microscopic level all energies are either Kinetic or potential as they are either created due to motion or particle interaction.

Raindrops fall on earth with certain kinetic energy on the earth. From where do they get this energy ?

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. Chemical energy

  2. Gravitational Potential energy

  3. Energy between molecules of water

  4. Heat energy

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Correct Option: B

Water stored in a dam primarily possesses

physics the essence of change forms of energy and energy conservation energy for everything forms of energy

  1. Heat energy

  2. Electrical energy

  3. Kinetic energy

  4. Potential energy

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Correct Option: D
Explanation:

Answer is D.

Potential energy is the energy that is stored in an object due to its position relative to some zero position. An object possesses gravitational potential energy if it is positioned at a height above (or below) the zero height.
There is potential energy stored in a water reservoir behind a dam. It is converted to kinetic energy when the water starts flowing down the penstock, from the dam. This kinetic energy is used to turn a turbine.
Hence, the water stored in a dam possesses potential energy.