English translation: moment and impulse (electromagnetics)/momentum (kinetics)
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GLOSSARY ENTRY (DERIVED FROM QUESTION BELOW)
German term or phrase:
Moment und Impuls
English translation:
moment and impulse (electromagnetics)/momentum (kinetics)
Explanation: Kraft = force
Moment = moment
Impuls = impulse or linear momentum or momentum (in kinetics)
Drehimpuls = angular momentum
Your context seems to be *mechanical* engineering so I shall limit myself to definitions in kinetics (a branch of physics that deals with motion and Newton's principles). [As a corollary, "Impuls" translates only to "impulse" in electromagnetic theory].
Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum which an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity.
momentum = mass x velocity
or (in symbols)
p = m x v
The units for momentum would be mass units times velocity units. The standard metric unit of momentum is the kg*m/s. From the definition of momentum, it becomes obvious that an object has a large momentum if either its mass or its velocity is large.
Consider a 0.5-kg physics cart loaded with one 0.5-kg brick and moving with a speed of 2.0 m/s. The total mass of loaded cart is 1.0 kg and its momentum is 2.0 kg*m/s. If the cart was instead loaded with three 0.5-kg bricks, then the total mass of the loaded cart would be 2.0 kg and its momentum would be 4.0 kg*m/s. A doubling of the mass results in a doubling of the momentum.
An object with momentum is going to be hard to stop. To stop such an object, it is necessary to apply a force against its motion for a given period of time. The more momentum which an object has, the harder that it is to stop. Thus, it would require a greater amount of force or a longer amount of time (or both) to bring an object with more momentum to a halt.
A force acting for a given amount of time will change an object's momentum. Put another way, an unbalanced force always accelerates an object - either speeding it up or slowing it down.
These concepts are merely an outgrowth of Newton's second law as (Fnet=m*a). It stated that the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the mass of the object. When combined with the definition of acceleration (a=change in velocity/time), the following equalities result.
F = m x a = m x [(delta)v / t]
or
F = m x [(delta)v/t]
If both sides of the above equation are multiplied by the quantity t, a new equation results.
F x t = m x (delta)v
In words, this equation could be said that the force times the time equals the mass times the change in velocity. In physics, the quantity Force*time is known as the impulse. And since the quantity m*v is the momentum, the quantity m*"Delta v" must be the change in momentum. The equation really says that the
Impulse = Change in momentum
-------------------------------------------------- Note added at 1 hr 7 mins (2003-11-09 15:09:32 GMT) --------------------------------------------------
You should remember that the German word \"Impuls\" translates to the English word \"impulse\" only in the context of electromagnetics, among other things, and *NOT* in kinetics. \"Impuls\" translates to \"momentum\" in kinetics. So if I back-translate the last equation above into German (impulse = change in momentum):
Explanation: Kraft = force
Moment = moment
Impuls = impulse or linear momentum or momentum (in kinetics)
Drehimpuls = angular momentum
Your context seems to be *mechanical* engineering so I shall limit myself to definitions in kinetics (a branch of physics that deals with motion and Newton's principles). [As a corollary, "Impuls" translates only to "impulse" in electromagnetic theory].
Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum which an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity.
momentum = mass x velocity
or (in symbols)
p = m x v
The units for momentum would be mass units times velocity units. The standard metric unit of momentum is the kg*m/s. From the definition of momentum, it becomes obvious that an object has a large momentum if either its mass or its velocity is large.
Consider a 0.5-kg physics cart loaded with one 0.5-kg brick and moving with a speed of 2.0 m/s. The total mass of loaded cart is 1.0 kg and its momentum is 2.0 kg*m/s. If the cart was instead loaded with three 0.5-kg bricks, then the total mass of the loaded cart would be 2.0 kg and its momentum would be 4.0 kg*m/s. A doubling of the mass results in a doubling of the momentum.
An object with momentum is going to be hard to stop. To stop such an object, it is necessary to apply a force against its motion for a given period of time. The more momentum which an object has, the harder that it is to stop. Thus, it would require a greater amount of force or a longer amount of time (or both) to bring an object with more momentum to a halt.
A force acting for a given amount of time will change an object's momentum. Put another way, an unbalanced force always accelerates an object - either speeding it up or slowing it down.
These concepts are merely an outgrowth of Newton's second law as (Fnet=m*a). It stated that the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the mass of the object. When combined with the definition of acceleration (a=change in velocity/time), the following equalities result.
F = m x a = m x [(delta)v / t]
or
F = m x [(delta)v/t]
If both sides of the above equation are multiplied by the quantity t, a new equation results.
F x t = m x (delta)v
In words, this equation could be said that the force times the time equals the mass times the change in velocity. In physics, the quantity Force*time is known as the impulse. And since the quantity m*v is the momentum, the quantity m*"Delta v" must be the change in momentum. The equation really says that the
Impulse = Change in momentum
-------------------------------------------------- Note added at 1 hr 7 mins (2003-11-09 15:09:32 GMT) --------------------------------------------------
You should remember that the German word \"Impuls\" translates to the English word \"impulse\" only in the context of electromagnetics, among other things, and *NOT* in kinetics. \"Impuls\" translates to \"momentum\" in kinetics. So if I back-translate the last equation above into German (impulse = change in momentum):
Kraftstoss = Impulsveraenderung
physics degree Greulich/Meenenga Woerterbuch der Physik
Marcus Malabad Canada Local time: 08:25 Works in field Native speaker of: English, Tagalog PRO pts in category: 11
Grading comment
very impressive answer! thanks a million, marcus!!!