Question Discussion & Solution

Rickshaw, bus and train are the means of transport.

Mobile and radio are the means of communication, so out of the given options only letter is a mean of communication.

Valency is the combining power of an element. Elements in the same group of the periodic table have the same valency.

Key Points

• Valency is the no of electron that looses, shared or gain to achieve stability or we can say to complete it outer most shell. 
• If any element has valence electron (electrons present in outer most shell) less than 4
  • ​​Valency = no of valance electron (valence electron<4)
• If any element has valence electron ​more than 4
  • ​​Valency = 8 - no of valance electron (valence electron>4)

​For Lithium:

• Li(Z=3) Electronic configuration = 2, 1
  • Valency = no of valance electron  = 1

​Hence, we can conclude that 1 is the valency of Lithium.

The correct answer is X-Ray.

• Electromagnetic (EM) radiation includes radiation via radio waves, microwaves, X-rays and gamma rays.

Key Points

• Electromagnetic (EM) radiation is a form of energy that is all around us and takes many forms.
• Electromagnetic (EM) radiation includes radiation via radio waves, microwaves, X-rays and gamma rays.
• Sunlight is also a form of EM energy.

​Additional Information

• ​EM radiation spans an includes a range of wavelengths and frequencies.
• This range is known as the electromagnetic spectrum.
• The EM spectrum is generally divided into seven regions:
  • Radio waves,
  • Microwaves,
  • Infrared (IR),
  • Visible light,
  • Ultraviolet (UV),
  • X-rays,
  • Gamma rays.

Important Points

• Radio waves have the longest wavelength.
• Gamma rays have the shortest wavelength.

A mountain range is a group or chain of mountains that are near together and formed by orogenic forces.

Important Points

• The Aravalli Range (sometimes called Aravali) is a mountain range in Northern-Western India.
• It runs roughly 670 kilometers (430 miles) from Delhi to Gujarat, going through southern Haryana and Rajasthan.
• Guru Shikhar, at 1,722 meters, is the tallest summit (5,650 ft).
• The Aravalli Range, which dates back to the Proterozoic era, is considered the world's oldest fold mountain system.

Additional Information

• Vindhya and Satpura ranges run parallel to each other and separate peninsular India from the mainland. 
• The Himalayas protect the Indian subcontinent from the North East as a natural barrier providing geopolitical benefits to the country.
• Vindhya, Satpura, and Himalayas are all young-fold mountains.

Hence, Aravallis is the oldest folded mountain in India.

Concept:

• Potential Energy: The energy of an object obtained by doing work against the conservative forces like spring force and gravitational force is called potential energy.
• The Gravitational potential energy of an object at a height h from the ground is given as

P = mgh

The spring potential energy of spring when it is stretched x distance from its natural length is given as

 \(P = \frac{1}{2}kx^2\)

• Kinetic Energy: The energy obtained by an object by virtue of its motion is called kinetic energy.

\(K = \frac{1}{2}mv^2\)

K is kinetic energy, v is the speed of the object, m is the mass of the object.

• Mechanical Energy: The sum of potential energy and kinetic energy is called mechanical energy.

Explanation:

So, from the above concept, it is clear that total mechanical energy is the sum of potential energy and kinetic energy. 

So, the answer is the Sum of Kinetic Energy and Potential Energy.