# Calculations#

mass (m) | <= | |

velocity (V) | <= | |

momentum (p) | => |

# Some facts#

- Momentum is a vector. Direction of momentum is the same as the direction of velocity of the body.
- Momentum has no dedicated unit in SI system. Instead, derivative units are used for example kilogram times meter per second:

$\dfrac{kg \times m}{s}$or newton times second:

$N \times s$ - Momentum of the system consisting of number of bodies (subsystem) is the (vector) sum of momentums of each individual objects (subsystems).
- If the sum of external forces in the inertial system is zero, then the momentum of the system is constant. In other words, the momentum changes if and only if there are unbalanced forces in the system. This rule is known as
**the principle of conservation of momentum**. - In classical physics, knowledge momentums and positions of all the particles at some time t
_{0}completely defines the state of the system. Moreover, we can calculate the state in any other time (both from the past and future), by solving motion equations. - The space in which the dimensions are momentums and locations is called the
**phase space**. Then, the state of the system is represented by a single point in this space.

- The dimension of phase space depends on
**number of degrees of freedom**. Adding new dimensions is redundant and leads to repeat information already contained.

- Changing the state of the system corresponds to the movement of a point in phase space.

- In other words - all classical physics is a
**single point moving in multidimensional space**!

- Phase space loses its original meaning in the transition to quantum mechanics. In this case the measurement momentums and positions at a time t
_{0}no longer defines the state of the system, because the state of the system is described by**a wave function**now. In other words, an analogue of phase space in quantum mechanics is**the wavefunctions space**.

- The dimension of phase space depends on
- The momentum concept has sense also with respect to field for example electromagnetic or gravity fields.
- Photon is a example of particle, which has momentum, but has no (rest) mass. Photon momentum is equal to:

$p = \dfrac{h}{\lambda}$gdzie:

- $h$ is the Planc constant,

- $\lambda$ is a photon wavelength.

- $h$ is the Planc constant,

# Momentum formula:#

$p = m \times v$

where:- p - momentum
- m - mass
- v - velocity (speed)

# Momentum formula solved for mass:#

$m = \dfrac{p}{v}$

# Momentum formula solved for velocity:#

$v = \dfrac{p}{m}$

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# Ancient version of this site - links#

In December 2016 the Calculla website has been republished using new technologies and all calculators have been rewritten. Old version of the Calculla is still available through this link: v1.calculla.com. We left the version 1 of Calculla untouched for archival purposes.

Direct link to the old version: "Calculla v1" version of this calculator

Direct link to the old version: "Calculla v1" version of this calculator