# Physics Formula for Class 9

Physics Formula for Class 9

Suppose three objects begin walking down a field of smooth, freshly fallen snow. Before anything begins, they begin to move in and out of range of each other. Imagine that we have a simple, yet full-scale version of this situation with coordinates for the movement of the objects: However, our situation is much more complex, and actually consists of many different trajectories:

L! E! H! What if we had to accept a different realization of this situation?

Suppose that we know at least one kind of motion, and maybe some other kinds that seem to be similar in movement. This generalized representation of the situation would not have enough variety to make it a three-dimensional space, so it could not be considered real.

Also Read:- Physics Formula for Class 10

In order to create the state we want with this generalized representation, we must leave open the door to some additional, far more complex eventual state (e.g., change from one direction to another), which is what the three-dimensional space is. Moreover, we might want to incorporate up to three different kinds of horizons, which as we could only imagine sounds like crazy, but by changing its direction from the origin, the larger distances go from between two points, which corresponds to changes in our long-range light.

The result would be much more complicated than the classic version of the situation that we took before.

## Relative Deviation

Relative Deviation = Means Deviation/ Mean Value × 100

## Prefixes:

 Prefixes Value Standard form Symbol Tera 1000000000000 10¹² T Giga 1000000000 10⁹ G Mega 1000000 10⁶ M Kilo 1000 10³ k deci 0.1 10-1 d centi 0.01 10-2 c milli 0.001 10-3 m micro 0.000001 10-6 μ nano 0.000000001 10-9 n pico 0.000000000001 10-12 p

## Units for Area and Volume

1m² = 10⁴ cm²   (10,000cm²)    1cm² = 10-4 m²  (1/10,000 m²)

1m³ = 10⁶ cm³   (1,000,000cm³)   1cm³ = 10-6 m³  (1/1,000,000m³)

## Force and motion

### Average Speed :

Average Speed = Total Distance/ Total Time

Velocity :

V = s/t

V = Velocity (ms-1)

s = displacement (m)

t = time (s)

Acceleration :

a = v – u / t

a = acceleration       (ms-2)

v = final velocity     (ms-1)

u = initial velocity    (ms-1)

t = time for the velocity change

(s)

## Momentum

p = m × v

p = momentum   (kg ms-1)

m = mass      (kg)

v = velocity     (ms-1)

Principle of Conservation of Momentum :

mu + m2u2 = m1v1 + m2v2

m₁ = mass of object 1

m₂ = mass of object 2

u₁ = initial velocity of object 1

u₂ = initial velocity of object 2

v₁ = final velocity of object 1

v₂ = final velocity of object 2

## Energy

### Kinetic Energy :

Ek = 1/2 mv²

Ek = Kinetic Energy  (J)

m = mass  (m)

v = velocity   (ms-1)

Gravitational Potential Energy :

Ep = mgh

Ep = Potential Energy   (J)

m = mass  (m)

g = gravitational acceleration    (ms-2)

Elastic Potential Energy :

E= ½ kx²

E=Potential Energy  (J)

k = spring constant  (Nm-1)

x = extension of spring  (m)

Ep = ½ Fx

F = Force  (N)

## Power and Efficiency

### Power :

P = W/t

P = E/t

P = power  (W)

W = work done  (J or Nm)

E = energy change  (J or Nm)

t = time  (s)

Efficiency :

Efficiency = Useful Energy/ Energy x 100%

Or

Efficiency = Power Output/Power Input x 100%

## Hooke’s Law

F = kx

F = Force  (N)

k = spring constant   (Nm-1)

x = extension or compression of spring   (m)

## Force and Pressure

ρ = m/v

ρ = density  (kg m-3)

m = mass  (kg)

v = volume  (m)

### Pressure :

P = F/A

P = Pressure  (Pa or N m-2)

F = Force acting normally to the surface (N)

A = Area of the surface (m2)

### Liquid Pressure :

P = hρg

h = depth  (m)

ρ = density  (kg m-3)

g = gravitational Field Strength  (N kg-1)

Pressure in Liquid :

P = Patm + hρg

h = depth (m)

ρ = density  (kg m-3)

g = gravitational Field Strength  (N kg-1)

Patm = atmospheric Pressure   (Pa or N m-2)