Question 1: Estimate (i) the momentum and (ii) the kinetic energy of the bird prior to hitting the window.
Question 2: Estimate (i) the force with which it hit the window, (ii) the pressure on the window during impact, and (iii) the wingspan of the bird, given that the wingtip-to-wingtip horizontal distance on the window was about 18 in. (∼46 cm).
Solutions to Question 1: (i) I estimate the weight of a typical adult pigeon (assuming it was a pigeon) to be m ≈ ½ kg, and speed in flight v ≈ 40 km/h or ∼10 m/s. Hence, the momentum was approximately 5 kg · m/s.
(ii) The kinetic energy ½mv2 ≈ 25 N·m.
Solutions to Question 2: (i) I think that 1 s is too long, and 0.025 s is too short, so the geometric mean is 0.2 s. If so, then the rate of change of momentum is (5 – 0)/0.2 = 25 N.
Note that I’ve assumed the bird suffers an inelastic collision; i.e., it doesn’t bounce back when it hits the window. If that were not the case, the force on the window (and the bird) would be greater.
(ii) I estimate the impact area (ignoring the slender wing cross sections) to be approximately 100 cm2 = 10−2 m2, so the pressure would have been, under these assumptions, equivalent to 25 × 102 = 2500 N/m2, or 2500 Pa. This is like a 250-kg person (500+ lb) standing on the glass if it was oriented horizontally.