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Mechanics
Published in W. David Yates, Safety Professional’s Reference and Study Guide, 2020
Momentum is a measure of the motion of a body equal to the product of its mass and velocity. We calculate the momentum by using the following equation: ρ=mv
The best driver in physics
Published in Jonathan Allday, Apollo in Perspective, 2019
The momentum of an object is defined as its mass multiplied by its velocity: Momentum = Mass × VelocityP = mv so any object that is not moving has zero momentum. Newton's laws can be used to prove that the total amount of momentum in the whole universe never changes. If we were able to add the momenta of every single object in the whole universe now and be able to calculate the same impossible sum a million years from now (or a million years ago for that matter), you would get exactly the same answer.
Modeling and virtual prototyping
Published in Fuewen Frank Liou, Rapid Prototyping and Engineering Applications, 2019
Conservation of momentum states that in the absence of external forces, a system will have constant total momentum. It is commonly used in collision models. A physics problem often requires the use of this fact in the collision of two elastic objects as shown in Figure 3.10. Due to momentum conservation, the sum of the momentum before the collision must equal the sum of the momentum after the collision: M1V1,i+M2V2,i=M1V1,a+M2V2,a
Relationships between Challenge Tour golfers’ clubhead velocity and force producing capabilities during a countermovement jump and isometric mid-thigh pull
Published in Journal of Sports Sciences, 2019
Jack E.T. Wells, Laura H. Charalambous, Andrew C.S. Mitchell, Daniel Coughlan, Simon L. Brearley, Roger A. Hawkes, Andrew D. Murray, Robert G. Hillman, Iain M. Fletcher
From Newton’s Second Law of Motion, it can be stated that impulse (force x time) is directly proportional to the change in momentum (mass x velocity). Since a golfer’s mass remains constant from shot to shot, it is the velocity that is affected through increasing the amount of force, or the time in which force acts during the downswing. Consequently, a golfer may increase impulse through pushing into the ground more (i.e. increasing vGRF) or by increasing the duration of their downswing, assuming no adverse reduction in mean force. This may be achieved by lengthening the backswing, or adopting a sequence that initiates the downswing from the ground-up. Along with these technical suggestions, golfers may also benefit from engaging in a resistance training and/or vertical jump interventions since previous research has indicated that these protocols have increased both impulse (Cormie, McGuigan, & Newton, 2010) and CHV (Doan et al., 2006, Fletcher & Hartwell, 2004). In addition, a recent investigation indicated that vertically oriented resistance training generated a statistically significant increase in vGRFs and ball velocity within highly skilled golfers (Driggers & Sato, 2017).
Experimental study on the hydrodynamic impact of tsunami-like waves against impervious free-standing buildings
Published in Coastal Engineering Journal, 2018
Davide Wüthrich, Michael Pfister, Ioan Nistor, Anton J. Schleiss
This quantity also represents the area of the surface below the curve, as shown in Figure 19. Given Newton’s second law (F = m∙a = m∙∆V/∆t), the impulse can be expressed as I = F∙∆t = m∙∆V, corresponding to the change in momentum. The impulse experienced by the building Itot equals therefore the exchange in momentum with the incoming wave. To better define the amount of impulse that is transferred to the building before the peak force occurs, a parameter, Ipeak, is defined as the integral between 0 < T < τmax. The latter represents the area of the surface below the curve up to the moment when Fx,max is recorded (Figure 19).
Monitoring residual 36 h post-match neuromuscular fatigue in rugby union; a role for postural control?
Published in European Journal of Sport Science, 2019
Jordan C. Troester, Rob Duffield
Current results report possibly small decreases in IMP-D and then IMP on both legs in the higher load group as based on specific thresholds for meaningful change (7–8%). This may suggest the clearest trend towards 36 h post-match impairment in the landing measures investigated in this study. However, no previous research provides evidence for the time-course for recovery of impulse measures from a single-leg landing task to contextualise this finding. Impulse is a measure of the area under the force-time curve (N.s) and represents change in momentum or force absorption during landing (Madigan & Pidcoe, 2003). Since changes in PF were likely trivial, the possible decreases in IMP in the current investigation support previous reports of altered landing strategy with shorter time to peak force resulting in lower impulse (James et al., 2010; Zadpoor & Nikooyan, 2012). This strategy could indicate NMF resulting in increased landing stiffness and reliance on connective tissues rather than the absorption of force through eccentric muscular contraction (Coventry et al., 2006). While speculative, this explanation coincides with reports of altered movement strategy in CMJ related to NMF following AFL matches and intensified periods of rugby union training (Cormack, Mooney, Morgan, & McGuigan, 2013; Gathercole, Sporer, & Stellingwerff, 2015). Given the possibly lower values 36 h post-match (especially in the higher load group) compared to rested states, IMP provides the most pronounced and longest lasting response of the landing measures investigated in this study. As a result, IMP may be useful for identifying altered landing strategy indicative of NMF and could be used to inform readiness to train at the beginning of a micro-cycle following a match.