157_Physics ProblemsTechnical Physics

157_Physics ProblemsTechnical Physics - Chapter 6 Q6.17 159...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 6 159 Q6.17 From the proportionality of the drag force to the speed squared and from Newton’s second law, we derive the equation that describes the motion of the skydiver: m dv dt mg DA v y y =− ρ 2 2 where D is the coefficient of drag of the parachutist, and A is the projected area of the parachutist’s body. At terminal speed, a dv dt y y == 0 and V mg T 2 12 F H G I K J . When the parachute opens, the coefficient of drag D and the effective area A both increase, thus reducing the speed of the skydiver. Modern parachutes also add a third term, lift, to change the equation to m dv dt mg v LA v y yx ρρ 22 where v y is the vertical velocity, and v x is the horizontal velocity. The effect of lift is clearly seen in the “paraplane,” an ultralight airplane made from a fan, a chair, and a parachute. Q6.18 The larger drop has higher terminal speed. In the case of spheres, the text demonstrates that terminal speed is proportional to the square root of radius. When moving with terminal speed, an
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .

Ask a homework question - tutors are online