Two steel thin-wall tubes in torsion of equal length are to be compared. the first is of square cross section, side length b, and wall thickness t. the second is a round of diameter b and wall thickness t. the largest allowable shear stress is tall and is to be the same in both cases.

Askydiver weighing 140 lb (including equipment) falls vertically downward from an altitude of 19,000 ft and opens the parachute after 18 s of free fall. assume that the force of air resistance, which is directed opposite to the velocity, is of magnitude 0.55|v| when the parachute is closed and is of magnitude 14|v| when the parachute is open, where the velocity v is measured in ft/s. assume that acceleration due to gravity has magnitude 32 ft/s/s; remember that weight is the product of mass and gravitational acceleration. (a) find the speed of the skydiver when the parachute opens. (b) find the distance fallen before the parachute opens. (c) what is the limiting velocity vl after the parachute opens? (d) determine how long the sky diver is in the air after the parachute opens. (e) plot the graph of velocity versus time from the beginning of the fall until the skydiver reaches the ground.

Akg a of 55 m at an of 11 ? . if is at 98 km/h,be ?

When a spring is compressed, the energy changes from kinetic to potential. which best describes what is causing this change? work power gravitational energy chemical energy