parallel axis theorem states that the moment of inertia about any axis is equal to the sum of moment of inertia about its centre of gravity and product of area and sqaure of pependicular distance from centre of gravity.

ie., 

I_aa= I_g + Ah²

It recoils due to conservation of momentum of system.
Iniatial momentum of gun = Final momentum of gun 
0 = m₁v₁ + m₂v₂
{tex}v_2 = -{m_1v_1 \over m_2}{/tex}
(-ve sign because velocity of gun is in opposite direction of bullet)

{tex}​​​​​​​Recoil \ velocity = -v_2 = {m_1v_1 \over m_2}{/tex}

Where 
m₁ and m₂ are masses of bullet and gun respectively 
v₁ and v₂ are velocity of bullet and gun respectively

1. The wheels of the bicycle each have their own angular momentum vectors, which like to stay pointed in the same direction, and hence resist tipping from side to side .

2. Since the bicycle is moving, any tipping to one side or the other can easily be corrected by turning the front wheel slightly to one side and getting a mv²/r force that will tend to counteract the tipping. The greater the  velocity, the bigger this force is.

Mass of box,m=40 kg
Distance from open end,s=5 m
Coefficient of friction, {tex}\mu{/tex}= 0.15
Acceleration of truck,a=2 ms^-2

Value of frictional force,f={tex}\mu mg{/tex} = {tex}0.15 \times 40 \times 10 = 60 N {/tex}
Working in frame of truck,
Pseudo force on block F=ma=(40)(2)=80 N
Acceleration of block,a= {tex}{F-f\over m} ={80-60\over 40}=0.5 \ ms^{-2}{/tex}

Let the time taken be t.

So,
{tex}5 = 0\times t + {1\over 2}\times a\times t^2 \\ => 5 = {1\over 2}\times 0.5\times t^2 \\ => t^2 = 20 \\ => t =\sqrt {20}{/tex}

Distance travlled by truck x = {tex}{1\over2 }\times a \times t^2 {/tex}

{tex}= {1\over 2} \times 2\times (\sqrt {20})^2 = 20 \ m {/tex}

Velocity Gradient is defined as rate of change in velocity per unit of distance. 

Velocity Gradient= velocity/distance.
Dimensional Formula of velocity= M⁰L¹T^-1
Dimensional Formula of Velocity Gradient = M⁰L⁰T^-1

SI unit of Velocity Gradient is s^-1

Stress- Strain Curve :It is a curve between stress and strain. A graph is plotted between the stress (which is equal in magnitude to the applied force per unit area) and the strain produced.
The graph helps us to understand how a given material deforms with increasing loads.
The curve between O and A, is a straight line. This means stress is directly ∝ to strain.
In this region Hooke’s Law is applicable.
In this region the material behaves like an elastic body.
In the region from A to B, stress and strain are not directly ∝. But still the material returns to its original dimension after the force is removed. They exhibit elastic properties.

1. Knowing the units of measurement that correspond with a number can give you so much more information than a digit sitting there by itself.
2. Help to show another person the exact amount you have
3. Assist in solving a mathematical problem, especially in chemistry, where you can follow the units to get to the answer
4. Show which measurement system the person is using (i.e. metric or standard).

Knowing the units of measurement that correspond with a number can give you so much more information than a digit sitting there by itself. Units can:

• Help to show another person the exact amount you have;
• Assist in solving a mathematical problem, especially in chemistry, where you can follow the units to get to the answer;
• Show which measurement system the person is using (i.e. metric or standard).

In a nutshell, the unit of measurement in science serves as the supporting pillar upon which a number rests.

Electromagnetic Force:It is a type of physical interaction that occurs between electrically charged particles .

A fundamental force in nature, the electromagnetic force(electrostatic force) acts between charged particles and is the combination of all electrical and magnetic forces.

For example, the electromagnetic force holds atoms together in molecules, causes friction, and attracts iron to a magnet.