Robert has just bought a new model rocket, and is trying to measure its flight c

Question

Robert has just bought a new model rocket, and is trying to measure its flight characteristics. The rocket engine package claims that it will maintain a constant thrust of 14.1 N until the engine is used up. Robert launches the rocket on a windless day, so that it travels straight up, and uses his laser range-finder to meaure that the height of the rocket when the engine cuts off is 14.6 m. He also measures the rocket's peak height, which is 19.1 m. If the rocket has a mass of 0.763 kg, how much work is done by the drag force on the rocket during its ascent? _____Joules

Explanation / Answer

as Rocket goes up there are three forces on it.

(thrust force, gravitational force and drag force )

Using workk energy theorem,

work done by gravitational force + work done by thrust + work done by drag = change in KE

- m g (h1 + h2) + Fthrust x h1 + Wdrag = 0 - 0

Wdrag = (0.763 x 9.8 x (14.6 + 19.1) ) - (14.1 x 14.6)

   = 46.13 J

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