You are on the roof of the physics building, 46.0 m above the ground (figure 1).

ID: 2271253 • Letter: Y

Question

You are on the roof of the physics building, 46.0 m above the ground (figure 1). Your physics professor, who is 1.80 m tall, is walking alongside the building at a constant speed of 1.20 m/s.

1.) If you wish to drop an egg on your professor''s head, how far from the building should the professor be when you release the egg? Assume that the egg is in free fall.

x = ?

I have no idea how to do this problem! Please show step by step with correct answers so I can try and understand.

THANK YOU!!

You are on the roof of the physics building, 46.0 m above the ground (figure 1). Your physics professor, who is 1.80 m tall, is walking alongside the building at a constant speed of 1.20 m/s. If you wish to drop an egg on your professor''s head, how far from the building should the professor be when you release the egg? Assume that the egg is in free fall. x = ? I have no idea how to do this problem! Please show step by step with correct answers so I can try and understand.

Explanation / Answer

Assuming you bend over to drop the egg from the edge of the roof (so we don't factor an additional height from the roof to your hand), the egg needs to fall a total of 46 meters minus the height of the prof

46 - 1.8 = 44.2 meters to fall

next you need to know how many seconds it will take gravity to pull the egg down that far, assuming you gently release it without any additional starting velocity (note: THROWING the egg would be even MORE fun for your professor) In this case, we use

d = 1/2 g * t^2

solve for t, since that is what we want

t = sqrt( 2d/g)

since our units are meters and seconds, we will use a value of g = 9.8 m/s^2

so,

t = sqrt( 2 * 44.2 / 9,8 )

for this we cheat and use a calculator to get

t = 3.0033, which we could probably just call 3 seconds

So, how far can your professor walk in that many seconds?

d = r * t = (1.2 m/s) * (3.0033s ) = 3.604 meters

Hence you should release the egg when your professor is 3.6 meters away from ground zero.

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You are on the roof of the physics building, 46.0 m above the ground (figure 1).

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