About forces and waves?
1) Small birds flap their wings rapidly to fly at a constant height. Explain in terms of forces why a kite(a bird) is able to fly at a constant height with only slight movements of its wings.
2) When a stem of a vibrating tuning fork touches the end of a stretched wire, a small piece of paper at the centre of the paper jumps off. This is an example of resonance.
i) Explain what is resonance in this case.
ii) State and explain one adjustment you could make to the wire to stop the paper jumping off when the tuning fork touches the wire.
P.S. I am preparing for my exams – please answer seriously
1. Birds flap wings to get forward motion. i suppose the geometry of the feathers might also change to help lift the bird on the downstroke more than the bird gets pushed down on the upstroke. The wing is an airfoil so that air going over the top must travel farther and therefore go faster than air that flows underneath. The faster moving air has lower pressure (Bernoulli principle) so the pressure difference lifts the wing and the bird.
2. i) The natural frequency of the string vibration is about equal to that of the tuning fork.
ii) Change the natural frequency by changing the tension or shortening the wire.
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