Tag: physics

Questions Related to physics

Before a rubber ball bounces off from the floor, the ball is in contact with the floor for a fraction of second. Which of the following statements are correct?

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

  1. Conservation of energy is not valid during this period

  2. Conservation of energy is valid during this period

  3. As ball is compressed, kinetic energy is converted to compressed potential energy

  4. None of these

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Correct Option: B
Explanation:

The law of conservation of energy is valid at any instant & in all circumstances.

According to law of conservation of energy the total energy of the universe is:

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

  1. Increasing

  2. Decreasing

  3. Remains constant

  4. Above law does not say anything about the universe

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Correct Option: C
Explanation:

Law of conservation of energy states that Energy can neither be created nor destroyed. Hence according to the law of conservation of energy the total energy remains constant. This law is applied everywhere in the universe.

According to the law of conservation of energy.

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

  1. energy exists in only one form

  2. energy can be created but no destroyed, and it can be transformed from one form to another

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

  4. energy can neither be produced nor be destroyed, it can only be transformed from one form to another form

Show answer
Correct Option: D
Explanation:

Law of conservation of energy.

The temperature of water at the bottom of a large waterfall is higher than that of the water at the top, because

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

  1. the falling water absorbs heat from the sun.

  2. the KE of the falling water is converted into heat.

  3. the water at the bottom has greater PE.

  4. rocks on the bed of the river give out heat.

Show answer
Correct Option: B
Explanation:

As the water falls, the Kinetic Energy of the water gets converted to heat energy increasing its temperature at the bottom than at the top.

Law of conservation of energy states that :

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

  1. energy cannot be destroyed but can be created and transformed from one form to another

  2. enerry 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 be transformed from one form to another

Show answer
Correct Option: D
Explanation:

The law of conservation of energy states that energy can neither be created nor be destroyed but it can be converted from one form to another i.e total energy in the universe will never change.

Eg:- Potential energy of a gas or oil is changed into energy to heat a building.

A thorium nucleus emits an alpha particle. Which of the following fundamental physics principles can be used to explain why the direction of the daughter nucleus recoil must be in the opposite direction of the alpha emission?
I. Newtons third law
II. Conversation of momentum
III. Conversation of energy

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

  1. Only II

  2. Only III

  3. I and II only

  4. II and III only

Show answer
Correct Option: C
Explanation:

By Newton's third law of motion, every action has equal and opposite reaction. Hence, the direction of the daughter nucleus recoil must be in the opposite direction to the direction of the alpha emission.


By law of conservation of momentum, the net momentum of the system should remain constant as no external force is acting on the system. Hence, momentum of the daughter nucleus must be opposite to the direction of the alpha particle so that the net momentum of the system remains zero.

By law of conservation of energy, the total energy of an isolated system remains zero. It cannot be used to conclude the direction of motion of the particles.

A ball is dropped from a height of $10\ m$. If the energy of the ball reduces by $40\%$ after striking the ground, how much high can the ball bounce back? $(g = 10 m s^{-2})$ :

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

  1. $6\ m$

  2. $4\ m$

  3. $10\ m$

  4. None of the above

Show answer
Correct Option: A
Explanation:

$M g h = M \times 10 \times 10 = 100 M\  J.$
Energy is reduced by $40\%$ then the remaining energy is $60M\ J$.
Then, $60M=M\times 10\times {h}'$

or, ${h}' = 6\ m$

A stone of mass $m$ kg is whirled in a vertical circle of radius $20$ cm. The difference in the kinetic energies at the lowest and the topmost position is:

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

  1. $4 \ mg\  joule$

  2. $0.4\ mg\ joule$

  3. $40 \ mg \ joule$

  4. None of these

Show answer
Correct Option: B
Explanation:

According to the law of conservation of energy 
Total energy of the system (KE $+$ PE) will be equal at both  , topmost and bottom most point.
Therefore, $\bigtriangleup PE =\bigtriangleup KE$
 $KE _{b}-KE _{t} = PE _{t} - PE _{b}$
$PE _{t} - PE _{b} = m\times g\times (2\times r)$
$\bigtriangleup KE = 0.4 \ mg$ $joule$

Heat energy produces a sensation of-

physics heat - measurement sources of heat introduction to heat measuring temperature

  1. warmth

  2. coldness

  3. both warmth and coldness

  4. none of these

Show answer
Correct Option: A
Explanation:
Heat energy is the result of the movement of tiny particles called atoms, molecules or ions in solids, liquids and gases. Heat energy can be transferred from one object to another. The transfer or flow due to the difference in temperature between the two objects is called heat.
Heat energy produces a sensation of warmth

State whether given statement is True or False
A wooden chair feels colder than an iron chair in winter

physics heat - measurement sources of heat introduction to heat measuring temperature

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Metal conducts heat much better than wood does. Since your hand is hotter than room temperature, both the metal and the wood conduct heat away from it.an iron chair in winter feels colder