Question

Falcons are known to protect their young by crashing into any bird that comes too close. If a 600g falcon flies vertically downward at 20 m/s into a 1.5 kg bird flying at 9 m/s horizontally, and the impact is perpendicular to the direction the other bird is flying, by what angle did the falcon change the other bird’s direction of motion? Give the angle measured from the horizontal. Assume the birds “stick together “ briefly after the collision.

Answer 1

By the conservation of momentum, Initial vertical momentum = final vertical momentum.

So, 0.6kg*20m/s = (0.6+1.5)*v*sin(theta) _________(A)

where v is the final velocity briefly after the collision of the birds stick together

Similarly, Initial horizontal momentum = final horizontal momentum.

So, 1.5kg*9m/s = (0.6+1.5)*v*cos(theta)___________(B)

(A) / (B) gives 0.6kg*20m/s / 1.5kg*9m/s = (0.6+1.5)*v*sin(theta) / (0.6+1.5)*v*cos(theta)

So, 12/13.5 = tan(theta)

So, theta = 41.63 degrees

So, the angle, measured from the horizontal, along which the falcon change the other bird’s direction of motion is 41.63 degrees