The average time it takes to repair headphones at a factory repair center is 90 hours with a standard deviation of 10 hours. To monitor this process daily, samples of 15 headphones are taken and the mean time computed. Today, the mean time was 84.5 hours. Suppose a similar sample of 15 headphones was undertaken shortly after the first sample was taken. The mean of both samples would be expected to be the same if the process is in-control.

If you were designing a bumper for a car, would you prefer it to exhibit elastic or plastic deformation? why? consider the functions of a bumper in both a minor "fender-bender" and a major collision.

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.

During a steady flow process, the change of energy with respect to time is zero. a)- true b)- false