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This type of impulse is often idealized so that the change in momentum produced by the force happens with no change in time. This sort of change is a step change , and is not physically possible. However, this is a useful model for computing the effects of ideal collisions (such as in videogame physics engines ).
For photons, this is the relation, discovered in 19th century classical electromagnetism, between radiant momentum (causing radiation pressure) and radiant energy. If the body's speed v is much less than c , then ( 1 ) reduces to E = 1 / 2 m 0 v 2 + m 0 c 2 ; that is, the body's total energy is simply its classical kinetic energy ...
If the net force experienced by a particle changes as a function of time, F(t), the change in momentum (or impulse J) between times t 1 and t 2 is = = (). Impulse is measured in the derived units of the newton second (1 N⋅s = 1 kg⋅m/s) or dyne second (1 dyne⋅s = 1 g⋅cm/s)
Alternatively, momentum and force can be represented as four-vectors. [83]: 107 Newton's third law must be modified in special relativity. The third law refers to the forces between two bodies at the same moment in time, and a key feature of special relativity is that simultaneity is relative.
The newton-second (also newton second; symbol: N⋅s or N s) [1] is the unit of impulse in the International System of Units (SI). It is dimensionally equivalent to the momentum unit kilogram-metre per second (kg⋅m/s). One newton-second corresponds to a one-newton force applied for one second.
Specific impulse (usually abbreviated I sp) is a measure of how efficiently a reaction mass engine, such as a rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the impulse, i.e. change in momentum, per mass of propellant. This is equivalent to "thrust per massflow".
The only pre-requisite for understanding impulse is that the reader has a rudimentary understanding of momentum. Impulse in its basic form is simply the difference between the initial momentum of an object, and its momentum at some later time. (In the case of rectilinear motion, both momentum and impulse can be treated as scalar quantities.
There are two main descriptions of motion: dynamics and kinematics.Dynamics is general, since the momenta, forces and energy of the particles are taken into account. In this instance, sometimes the term dynamics refers to the differential equations that the system satisfies (e.g., Newton's second law or Euler–Lagrange equations), and sometimes to the solutions to those equations.