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For example, a 1 kg model airplane, traveling due north at 1 m/s in straight and level flight, has a momentum of 1 kg⋅m/s due north measured with reference to the ground. Many particles The momentum of a system of particles is the vector sum of their momenta.
Then the angular equation in the momentum equations and the continuity equation are identically satisfied. The radial momentum equation reduces to ∂p / ∂r = 0, i.e., the pressure p is a function of the axial coordinate x only. For brevity, use u instead of . The axial momentum equation reduces to
v 1 is the initial velocity of the object when the time interval begins. Impulse has the same units and dimensions (MLT −1) as momentum. In the International System of Units, these are kg⋅m/s = N⋅s. In English engineering units, they are slug⋅ft/s = lbf⋅s. The term "impulse" is also used to refer to a fast-acting force or impact.
The radiation pressure again can be seen as the transfer of each photon's momentum to the opaque surface, plus the momentum due to a (possible) recoil photon for a (partially) reflecting surface. Since an incident wave of irradiance I f over an area A has a power of I f A , this implies a flux of I f / E p photons per second per unit area ...
On the other hand, the pressure in thermodynamics is the opposite of the partial derivative of the specific internal energy with respect to the specific volume: (,) = (,) since the internal energy in thermodynamics is a function of the two variables aforementioned, the pressure gradient contained into the momentum equation should be explicited ...
The moment of force, or torque, is a first moment: =, or, more generally, .; Similarly, angular momentum is the 1st moment of momentum: =.Momentum itself is not a moment.; The electric dipole moment is also a 1st moment: = for two opposite point charges or () for a distributed charge with charge density ().
The effect of the pressure gradient on the flow is to accelerate the flow in the direction from high pressure to low pressure. As written in the Cauchy momentum equation, the stress terms p and τ are yet unknown, so this equation alone cannot be used to solve problems.
The equation above presupposes that the gas density is low (i.e. the pressure is low). This implies that the transport of momentum through the gas due to the translational motion of molecules is much larger than the transport due to momentum being transferred between molecules during collisions.