Momentum and Impulse: Definition, Theorem and Examples - Video & Lesson Transcript | balamut.info
Impulse, Momentum, and Energy – Concepts The quantity Fdt is defined as Impulse, and the relationship between the change in momentum and the Impulse . Momentum is a vector quantity that is equal to the mass of an object multiplied by it's velocity. Momentum This is the relation between Impulse and momentum. Derive the relation between impulse and momentum. Asked by Lôrd Vivek Singh 6th March , PM. Answered by Expert. Answer: The effect of a force.
The term momentum is a physics concept. Any 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 that 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 such an object to a halt. As the force acts upon the object for a given amount of time, the object's velocity is changed; and hence, the object's momentum is changed.
Impulse & Momentum - Summary – The Physics Hypertextbook
The concepts in the above paragraph should not seem like abstract information to you. You have observed this a number of times if you have watched the sport of football. In football, the defensive players apply a force for a given amount of time to stop the momentum of the offensive player who has the ball. You have also experienced this a multitude of times while driving.
As you bring your car to a halt when approaching a stop sign or stoplight, the brakes serve to apply a force to the car for a given amount of time to change the car's momentum. An object with momentum can be stopped if a force is applied against it for a given amount of time. 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.
If the force acts opposite the object's motion, it slows the object down. If a force acts in the same direction as the object's motion, then the force speeds the object up.
Either way, a force will change the velocity of an object. And if the velocity of the object is changed, then the momentum of the object is changed. Impulse These concepts are merely an outgrowth of Newton's second law as discussed in an earlier unit. To truly understand the equation, it is important to understand its meaning in words.
In words, it could be said that the force times the time equals the mass times the change in velocity. Since acceleration is the first derivative d of velocity with respect to time, the equation can also be written to reflect the first derivative with respect to time rate of change in the quantity mv.
In such a case linear momentum L is expressed as equation 2. When a force acts upon the object from a time period from t1 to t2, equation 1 can be integrated in time to obtain equation 3.
What are momentum and impulse?
Equation 3 defines linear impulse Iand is equal to the change in linear momentum, as shown in equation 4. As mass is constant during free-weight resistance training, a greater impulse will result in a greater velocity. In human movement, force is required first to maintain static equilibrium and second to generate acceleration.
The force required to maintain static equilibrium is equal to an object's mass multiplied by gravitational acceleration. Additional force results in acceleration of a mass or a change in momentum. These components of acceleration are described in equation 5: Therefore, as generation of force greater than the weight of the resistance increases i.
As velocity approaches zero, propulsive force approaches zero, therefore slow moving objects only require force approximately equal to the weight of the resistance. The slower the intended velocity, the closer the force expressed comes to equalling the linear inertia of the load i. From Equation 1force is inversely proportional to time. That is, to perform a movement in a shorter period of time, greater force must be generated.
Arguments have been made that the muscle tension will be constant through the given range of motion, and thus provide optimum stimulation throughout such range Wescott, This statement has not been experimentally verified and unfortunately neglects the changes in moment arm and muscle length which ultimately change the muscle force regardless of speed of action.
This argument does, however, have some factual basis, as the impulse increases as time increases Equation 4in the case of maximal effort actions. In the case of PS, increasing time decreases force, and excessive time duration will not maximize impulse. Arguments for purposefully slow PS training Muscle force: While PS proponents vary in their reasoning for suggesting this method, the basic premise is that when the weight is moving quickly, the muscles will not be able to exert as much force and thus the training effect will be diminished Brzycki, ; Wescott, While true that the muscles will not produce as much force at the higher velocities during maximum effort velocity-controlled actions, the previous statement ignores the requisite force to initiate high velocity movements for a given load in an isoinertial condition.
In addition, the aforementioned F-V relationship was derived under conditions of maximal acceleration maximal voluntary muscle activationand thus differs from intentionally slow movements.
An attempt to reduce the speed of motion subsequently reduces the force expressed Keogh et al. Modifications to any one of these metabolic factors during exercise may alter signal transduction pathways and hence modify gene transcription for muscle growth Rennie et al.
What are momentum and impulse? (article) | Khan Academy
Potential strength adaptations due to acute metabolic stimuli have recently been reviewed elsewhere Crewther et al. The metabolic hypothesis has not yet been examined in conjunction with PS training studies; therefore these ideas are currently speculative for this type of training. Movements performed at low velocities prolong the time of contraction in each repetition for a given range of motion time-under-tension; TUT.
Proponents of PS training regard this increased time as a positive characteristic to stimulate training adaptation Wescott et al. TUT can be considered a manner by which to prescribe a dose of resistance exercise Tran and Docherty,which is crucial as the optimal dose for weight training is subject to tremendous debate Carpinelli and Otto, ; Stone et al.
PS advocates suggest that this time dose or TUT is of greater importance than the actual load lifted, which could be related to the fact that perceived effort in PS and normal training session have been shown to be similar Egan et al. This rationale originates from the hypothesis of a direct relationship between the duration of contraction and metabolic stimulus, but this hypothesis has not been supported in studies examining PS exercise Gentil et al. A potential caveat of increased TUT is that the load must be decreased to perform a successful s concentric contraction as compared to a maximal acceleration repetition i.
This is concerning as the load, or mechanical stimuli, has been suggested to be of critical importance for inducing adaptation Dudley et al. However, the reduced load advocated by PS might be less effective for hypertrophy due to the load constraints. This reduction in load is seen by PS advocates as inconsequential to the ultimate physiological effects. However, a basic premise of tissue adaptation i.
Wolff's and Davis' Laws Biewener and Bertram, is that a minimum threshold of force is required to elicit adaptation. The notion that load is peripheral in its importance is in direct opposition to other authors' demonstrating the magnitude of mechanical stress i.
Please note that although related, load and muscle force are not equal, as propulsive forces can differ.
Increasing TUT for an exercise session can be accomplished by simply increasing the number of total repetitions of maximal-acceleration exercises increased volume-load; Tran and Docherty, This would ultimately increase the time that the muscle has been under tension for that session, but the force output of the muscle will have been greater due to the relatively larger loads.
The complex relationship between load and TUT requires further investigation. Forms of resistance training fall within a continuum from slow to fast velocities. Resistance training such as powerlifting relatively slow and weightlifting relatively fast are quite far apart on this continuum.