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Assuming Newton's second law in the form F = ma, fictitious forces are always proportional to the mass m. The fictitious force that has been called an inertial force [7] [8] [9] is also referred to as a d'Alembert force, [10] [11] or sometimes as a pseudo force. [12] D'Alembert's principle is just another way of formulating Newton's second law ...
A form of Newton's second law, that force is the rate of change of momentum, also holds, as does the conservation of momentum. However, the definition of momentum is modified. Among the consequences of this is the fact that the more quickly a body moves, the harder it is to accelerate, and so, no matter how much force is applied, a body cannot ...
The SI unit of impulse is the newton second (N⋅s), and the dimensionally equivalent unit of momentum is the kilogram metre per second (kg⋅m/s). The corresponding English engineering unit is the pound-second (lbf⋅s), and in the British Gravitational System, the unit is the slug-foot per second (slug⋅ft/s).
Newton's second law of motion states that the rate of change of a body's momentum is equal to the net force acting on it. Momentum depends on the frame of reference , but in any inertial frame it is a conserved quantity, meaning that if a closed system is not affected by external forces, its total momentum does not change.
Equivalently, the differential form of Newton's Second Law provides an alternative definition of torque: [49] =, where is the angular momentum of the particle. Newton's Third Law of Motion requires that all objects exerting torques themselves experience equal and opposite torques, [50] and therefore also directly implies the conservation of ...
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.
So long as the force acting on a particle is known, Newton's second law is sufficient to describe the motion of a particle. Once independent relations for each force acting on a particle are available, they can be substituted into Newton's second law to obtain an ordinary differential equation, which is called the equation of motion.
Newton's second law of motion relates external forces to the change in linear momentum of the whole system (including rocket and exhaust) as follows: = where is the momentum of the rocket at time =: = and is the momentum of the rocket and exhausted mass at time =: = (+) + and where, with respect to the observer: