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# Constant forces watch

(see attached image - sorry its upside down!)
Thanks! x
2. (Original post by razzy02)
(see attached image - sorry its upside down!)
Thanks! x
As the aircraft moves along the runway, it is accelerating (F=ma) and therefore it's velocity is increasing. This means that that the 'drag' (D) force acting on it increases, because drag is (approx.) proportional to the square of velocity. So the 'net force' on the aircraft is F-D. As the velocity increases, drag increases and the net force becomes smaller and smaller, eventually equalling zero.
In other words, as the velocity increases the acceleration decreases, since acceleration = net force / mass
3. (Original post by rashid.mubasher)
As the aircraft moves along the runway, it is accelerating (F=ma) and therefore it's velocity is increasing. This means that that the 'drag' (D) force acting on it increases, because drag is (approx.) proportional to the square of velocity. So the 'net force' on the aircraft is F-D. As the velocity increases, drag increases and the net force becomes smaller and smaller, eventually equalling zero.
In other words, as the velocity increases the acceleration decreases, since acceleration = net force / mass
Thank you so much! This is an excellent explanation xx

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