Ultralight Cable
Ultralight Cable
Physics
.. average power?
Some gliders are launched from the ground by means of a winch, which rapidly reels in a towing cable attached to the glider. What average power must the winch supply in order to accelerate a 168-kg ultralight glider from rest to 24.5 m/s over a horizontal distance of 42.9 m? Assume that friction and air resistance are negligible, and that the tension in the winch cable is constant.
Change in kinetic energy is
deltaKE = delta(1/2 mv^2) = 1/2 (168 kg)(24.5 m/s)^2 - 1/2 (168 kg)(0 m/s)^2
Average speed is = 1/2 (168 kg)(24.5 m/s)^2 / t It's absurd though to ignore air resistance when you're towing a glider. Give your instructor a well-deserved kick in the pants for asking this foolish question. u
Time to launch is distance / average speed: t = (42.9 m) / (12.25 m/s)
Average power is deltaKE / time:


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