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Energy Today
Published in Anco S. Blazev, Global Energy Market Trends, 2021
In physics, the Newton’s second law is used to clarify that the net force acting upon an object is equal to the rate at which its momentum changes. Or, acceleration of an object is directly proportional to the net force acting on it; is in the direction of the net force, and is inversely proportional the mass of the object.
Linear motion
Published in William Bolton, Engineering Science, 2020
If the velocity of an object is measured at different times then a velocity– time graph can be drawn. Acceleration is the rate at which the velocity changes. Thus, for the graph shown in Figure 4.9, the velocity changes from v1 to v2 when the time changes from t1 to t2. Thus the acceleration over that time interval is (v2 – v1)/(t2 – t1). But this is the gradient of the graph. Thus:acceleration=gradient of the velocity−time graph
Linear and angular motion
Published in John Bird, Science and Mathematics for Engineering, 2019
The unit of linear acceleration is metres per second squared (m/s2). Rewriting equation (7) with v2 as the subject of the formula gives: v2=v1+ at
Techniques to derive and clean acceleration and deceleration data of athlete tracking technologies in team sports: A scoping review
Published in Journal of Sports Sciences, 2022
Susanne Ellens, Kane Middleton, Paul B. Gastin, Matthew C. Varley
The application of acceleration data as a measure of an athlete’s physical performance is common practice in team sports (Bradley et al., 2010; Cunningham, 2016; Fox et al., 2020; Gabbett, 2010; Kelly et al., 2019). Acceleration can be defined as the rate of change of velocity over time, where positive acceleration is an increase in velocity whilst negative acceleration is a decrease in velocity (better known and referred to in this paper as deceleration). Researchers and practitioners are interested in quantifying high rates of acceleration and deceleration (e.g., > ± 2 m · s−2, > ± 3 m · s−2, etc) as they are considered more energetically demanding than when they are low (Osgnach et al., 2009) and may have a critical impact on a player’s performance. High rates of acceleration and deceleration, for example, allow a player to reach the ball before an opponent or stop in time to avoid a tackle. In team sports, athletes frequently accelerate and decelerate at a high rate as the nature of the game requires many changes of a player’s velocity over a short duration (Harper et al., 2019a). Australian football players, for example, perform on average 82 high acceleration efforts (≥2.78 m · s−2) in a single match (Varley et al., 2014). Therefore, team sports researchers and practitioners monitor acceleration and deceleration during training and games for quantifying training load, injury prevention and performance enhancement (Akenhead & Nassis, 2016; Harper et al., 2019b) as they occur frequently, are energetically demanding and are considered important to assess athletes’ performance.
Investigating the potential of using glass foam for an EMAS material to mitigate aircraft overrun accidents
Published in International Journal of Pavement Engineering, 2021
The aircraft acceleration profile graphs for the B727-100 and B747-100 are shown in Figure 11. The negative acceleration indicates deceleration. For the B727-100 aircraft, both the SGAS and ARRESTOR results show similar behaviour with the ARRESTOR plot showing slightly greater deceleration. Deceleration shows a significant increase after the main landing gear enter the EMAS. Aircraft deceleration increases as the EMAS bed thickness increases. The acceleration profile for the B747-100 is very similar between the two computer codes. ARRESTOR calculates a larger deceleration as the main gear enter the EMAS and the EMAS thickness increases from 229 mm (9-in) to 610 mm (24-in). The maximum deceleration value is important when considering passenger safety. Typically, an absolute maximum deceleration value less than 1.0 g is considered acceptable, which is the case for this example.
Relative and absolute reliability of shank and sacral running impact accelerations over a short- and long-term time frame
Published in Sports Biomechanics, 2022
Aoife Burke, Sarah Dillon, Siobhán O’Connor, Enda F. Whyte, Shane Gore, Kieran A. Moran
Thus far, there are relatively few studies, which have explored the reliability of impact accelerations during running, with the majority of studies focusing on the magnitude of impact acceleration (Peakaccel) at the shank (Hughes et al., 2019; Sheerin et al., 2018; Van den Berghe et al., 2019). Only two studies to date have looked at the reliability of shank Peakaccel at and beyond one week (Sheerin et al., 2018; Van den Berghe et al., 2019), with only one of those extending to a long-term time frame of six months (Sheerin et al., 2018). The choice of tibial Peakaccel is presumably due to the high prevalence of lower limb injuries in running. However, only one study has investigated the reliability of Peakaccel at the sacrum over a one-day period (Lindsay et al., 2016), despite more proximal injuries being common in running (e.g., lower back injuries) (Ellapen et al., 2013). To further compound the paucity of research in this area, no studies have examined the reliability of the rate of acceleration (Rateaccel) for the shank or sacrum. As stated previously, force is the product of mass and acceleration, thus acceleration is directly proportional to force. Given that the rate of force development has been shown to be more related to RRI than the peak (Van Der Worp et al., 2016), there is possibly a need to examine the rate of acceleration (technically referred to as jerk) in RRI research. This study referred to jerk as Rateaccel so that there is better alignment and ease of interpretation. First and foremost, however, it is imperative to investigate the consistency of impact accelerations over both short- (e.g., 1 week) and long-term (e.g., 6 months) time frames.