To protect their young in the nest, peregrine falcons will fly into birds of pre

Question

To protect their young in the nest, peregrine falcons will fly into birds of prey (such as ravens) at high speed. In one such episode, a 650g falcon flying at  20.0m/s hit a 1.40kgraven flying at 9.0m/s . The falcon hit the raven at right angles to its original path and bounced back at 5.0m/s . (These figures were estimated by the author as he watched this attack occur in northern New Mexico.)

A) By what angle did the falcon change the raven's direction of motion?

B) What was the raven's speed right after the collision?

Explanation / Answer

Assuming a perfectly elastic collision with no loss in momentum, we apply the law of conservation of momentum.

We know that the raven and the falcon are flying at right angles to each other.

Assuming the falcon is flying east-west and the raven is flying north-south

The initial momentum of the system:

Momentum of falcon + Momentum of raven = 0.65X20 + 1.4 X 9 = 25.6 kg-m/s

Now, we know that the velocity of the falcon after the collision = 5m/s

Hence the momentum of the falcon after the collision = 5*0.65=3.25 kg-m/s

Since, there is conservation of momentum, hence:

Momentum of raven = 25.6-Momentum of falcon=25.6-3.25=22.35kg-m/s

Hence, the resultant velocity of the raven = 22.35/1.4=15.96 m/s

Now, we know that the north-south component of the raven remains unchanged at 9m/s

Hence, after the collision, an east-west component would be added which results in the alteration of the additional path by a certain angle "x".

x = cos-1(9/15.96)=55.68 degrees from the north-south line, moving in the north-east direction

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