Explanation

Bohr's quantum condition states that the angular momentum of an electron in a circular orbit is quantized:

mvr = nh / 2π

where m is the mass of the electron,

v is the velocity,

r is the radius of the orbit,

n is the principal quantum number,

and h is Planck's constant.

Explanation

The momentum 

𝑝 of a photon is given by the equation:

𝑝=ℎ/𝜆 

where:

h is Planck's constant,

λ is the wavelength of the photon.

Since photons are massless, their momentum is not related to mass but to their wavelength.

Explanation

An electron volt (eV) is a unit of energy.

It is defined as the amount of kinetic energy gained or lost by a single electron when it is accelerated through an electric potential difference of one volt.

Specifically:

1eV=1.602×10 −19 Joules

Thus, the electron volt is a convenient unit for measuring small amounts of energy, particularly in the fields of atomic and particle physics.

Explanation

• Alternating Current (AC) is the flow of electric charge that periodically changes direction.
• This type of current is commonly used in power distribution systems and household electrical outlets.

Explanation

• Atmospheric pressure is a scalar quantity that acts equally in all directions, pressing on surfaces from all sides.
• This is why a balloon expands in all directions when inflated, and why a submarine is squeezed from all sides by the surrounding water pressure.

Explanation

• Hydraulics is a branch of science and engineering that focuses on the use of liquids to transmit power, generate motion, and control systems.
• It is widely used in various industries, including construction, manufacturing, and aerospace.

Explanation

• The electrons that have been knocked out of the outermost shell of an atom are free electrons, which are able to move freely and conduct electricity.

Explanation

• The Sun is approximately 109 times larger than the Earth in terms of diameter.
• The Sun's diameter is about 1,392,684 kilometers (865,374 miles).
• The Earth's diameter is about 12,742 kilometers (7,918 miles).
• So, if you were to line up 109 Earths side by side, they would roughly equal the diameter of the Sun.

Explanation

• When you run a plastic comb through your dry and non-oily hair, the comb becomes statically charged.
• This static charge causes the comb to attract small, light objects like bits of paper.
• When you hold the comb above the paper, the paper is attracted to the comb due to the electrostatic force.

Explanation

• Wear and Tear is not an advantage of friction.
• It's a disadvantage, as friction causes wear and tear on surfaces.

Advantages of Friction:

• Walking: Friction between the soles of our shoes and the ground allows us to walk without slipping.
• Braking: Friction between the brake pads and the wheels allows vehicles to slow down and stop.
• Securing knots: Friction between the fibers of a rope helps keep knots tight and secure.
• Fasteners: Friction between threads in screws and bolts helps keep them in place and secure