Find the speed of a rock which is thrown off the top of a 20 m tall building at 15 m/s when it makes contact with a bird which is flying at an altitude of 10 m above the ground

Question

Physics

Martin Moran

10 May, 08:18

Find the speed of a rock which is thrown off the top of a 20 m tall building at 15 m/s when it makes contact with a bird which is flying at an altitude of 10 m above the ground

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Thalia Wiley · Answer 1

The vertical velocity of the ball when it is just thrown off the building is 15 m/s. It travels for 10 m before making contact with a bird. The ball is accelerated by the acceleration due to gravity, g. Using the kinematic equation, we have:

vf^2 = vi^2 + 2*a*d. So, vf^2 = (15 m/s) ^2 + 2 * (9.81 m/s^2) * (10 m)

Solving this, we have vf^2 = 421.2 m^2/s^2, vf = sqrt (421.2 m^2/s^2) = 20.5 m/s.

So its speed when it makes contact with the bird is 20.5 m/s