Deceleration distance

In the. preceding example, a, 500 g. tj - t, = 10 ms. The impulse repre.sented as a solid line is- approximately equivalent to the rectangular ampUtude impulse 0.66 a. This impulse can be used for calculating the deceleration distance, which i.s, . . , ... 

OSHA has not changed free fall and deceleration distance limits. These easily understood objectives provide good guidelines for our workers. However,... 

There are interpretation letters posted on the OSHA website stipulating that when you meet these objectives, OSHA will accept greater free fall and deceleration distances. The Z359.13 standard was written, in part, to provide equipment that meets (he first objective. This article focuses on how this equipment affects (he second. 

Deceleration distance means the additional vertical distance a falling employee travels, excluding lifeline elongation and free fall distance, before stopping, from the point at which the deceleration device begins to operate. It is measured as the distance between the location of an employee s body belt or body harness attachment point at the moment of activation (at the onset of fall arrest forces) of the decelera-... 

Free fall distance means the vertical displacement of the fall arrest attachment point on the employee s body belt or body harness between onset of the fall and just before the system begins to apply force to arrest the fall. This distance excludes deceleration distance, and lifeline/lanyard elongation, but includes any deceleration device slide distance or self-retracting lifeline/lanyard extension before they operate and fall arrest forces occur. 

B) For deceleration device systems with integral lifelines or lanyards which automatically limit free fall distance to 2 feet (0.61 m) or less, the test weight should free fall a distance equal to that permitted by the system in normal use. (For example, to test a system with a self-retracting lifeline or lanyard, the test weight should be supported and the system allowed to retract the lifeline or lanyard as it would in normal use. The test weight would then be released and the force and deceleration distance measured). 

The maximum elongation and deceleration distance should be recorded during the force test. 

The deceleration distance measured for deceleration devices during the force test ... 

Manufacturers also require that workers not work at a level where the point of snaphook attachment to the body harness is above the device because this will increase the free fall distance and the deceleration distance and will cause higher forces on the body in the event of an accidental fall. 

Limit a maximum arresting force on an employee to 1,800 pounds when used with a body harness (3) Bring an employee to a complete stop and limit maximum deceleration distance an employee travels to 3.5 feet and (4) Have sufficient strength to withstand twice the potential impact energy of an employee... 

Fig. 1. Deceleration and penetration curves from dynamic impact tester. Time vs distance penetrated (A) and deceleration (B). Distance between vertical...

Closure at the instant of reversal of flow is most nearly attained in these valves. This timing of closure is not the whole solution to noise and shock at check valves. For example, if cessation of pressure at the inlet of a valve produces flashing of the decelerating stream downstream from the valve or if stoppage of flow is caused By a sudden closure of a valve some distance downstream from the check valve and the stoppage is followed by returning water hammer, slower closure may be necessary. For these applications, tilting-disk check valves are equipped with external dashpots. They are also available with low-cost insert Dodies. 

Tool Deceleration (g. G) Time (ms) Braking Distance (m) Initial Velocity (m/s)... 

Taking into account the spring only compute the distance traveled x and the ma.ximum deceleration a in g s when the housing stops abruptly. 

For a typical sodium atom, the initial velocity in the atomic beam is about 1000 m s1 and the velocity change per photon absorbed is 3 crn-s. This means that the sodium atom must absorb and spontaneously emit over 3 x 104 photons to be stopped. It can be shown that the maximum rate of velocity change for an atom of mass m with a photon of frequency u is equal to hu/lmcr where h and c are Planck s constant and the speed of light, and r is the lifetime for spontaneous emission from the excited state. For sodium, this corresponds to a deceleration of about 106 m s"2. This should be sufficient to stop the motion of 1000 m-s 1 sodium atoms in a time of approximately 1 ms over a distance of 0.5 m, a condition that can be realized in the laboratory. 

Processes accompanied by a decrease in volume, such as C—C bond formation, in which the distance between two carbon atoms decreases from the van der Waals distance of ca 3.6 A to the bonding distance of ca 1.5 A, are accelerated by raising the pressure and equilibria are shifted toward the side of products (AV < 0, AV < 0). The reverse reaction, a homolytic bond cleavage, leads to an increase in volume (AV / > 0, AV > 0). Pressure induces a deceleration of such a process and a shift in equilibrium toward the side of reactants. However, in an ionization, such as an ionic dissociation, the attractive interaction between the ions generated and the solvent molecules leads to a contraction... 

It should be noted, however, that some of the tendencies described above may become invalid for very small droplets (for example, smaller than 10 pm under conditions in Ref. 156). Such small droplets may require a longer flight time to a given axial distance far from the atomizer due to the high deceleration, and their cooling rates may decrease as a result of the reduced relative velocity and temperature. In addition, the two-way coupling 576] may affect the momentum and heat transfer between atomization gas and droplets so that the droplet behavior may be different from that discussed above, particularly the radial distributions of droplet sizes and velocities. 

Separating the variables involved and integrating the equations between Mpo and 0, the distance the particle traveled in the first decelerating stage, i.e., the maximum depth of penetration into the opposed stream, xmax, can be obtained as... 

As mentioned above, in impinging streams, it is possible for the particle to penetrate to and fro many times between the two opposing streams. In other words, it would experience multiple decelerations-accelerations of motion. The time for each deceleration or acceleration motion, ruj or /aci (i = 1, 2, ) can be analyzed and calculated with the same principles and procedures as described above. Of course, the distance the particle travels in each of the deceleration stages,. v,u, can also be calculated however, those distances lack of significance, except for that in the first deceleration stage,. vdj =. vmav... 

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