If 10 lbs of bricks and 160 ozs. of feathers are dropped off the Empire State Building, which will land first?

Answer 1

As they are both the same weight (W), they have the same mass. This results because W = mg = Mg = W; where m is the mass of the bricks and M is the mass of the feathers; g is the acceleration due to gravity. Thus, m = M.

So the question is do these to objects accelerate to smack on the unsuspecting pedestrians below at different or the same rates? If they both accelerate at the same rate (say g for example), they will hit Aunt Suzy on the head at the same time because, as we all know, v^2 = 2gS when the initial velocity is u = 0. Thus, when both are dropping S distance, they both will reach the same velocity v when Aunt Suzy is done in. As t = S/v, that means both will take the same time t to land on her head. That results if and only if both accelerate at the same rate (e.g., g).

But, and this is a BIG BUT, what if they accelerate a different rates? Clearly their end velocities on impact will also be different. Their acclerations will differ if their net weights (w) are different. w = W - F = ma; where W = mg as before and F is a force acting in opposition to the weight of the bricks or feathers.

In air (the air around the Empire State Building), such a counteracting force is the drag force = 1/2 rho Cd A v^2 = F; where rho is air density, Cd is drag coefficient, A is cross sectional area, and v is still velocity. If the drag forces between the bricks and feather are different then clearly their net or effective weights will be different. In math talk w(b) = W - F(b) <> W - F(f) = w(f) because the brick drag force (F(b)) does not equal the feathers drag force (F(f))

Lest you think the drag force on the feathers needs to be greater than that on the bricks, think again. Suppose the feathers were packaged in a shape similar to the shape of the package of bricks. And the wrappings for both packages are made of the same material. In this case, their respective coefficients of drag (Cd) and their cross sectional areas (A) would be the same. Which means F(b) = 1/2 rho Cd A v^2 = F(f) and therefore w(b) = ma = Ma = w(f) so that, once again, they'd hit Aunt Suzy at the same time.

So the answer to your question, as is usual in physics, it depends. It depends on how the feathers and bricks are packaged. If they are packaged so their respective Cd's and A's are the same, they will hit the pedestrians at the same time; otherwise, they will probably be at different times.

Answer 2

10lbs of bricks and 10lbs of feathers (160 oz) would only fall at the same speed in a vacuum, *or* if the feathers were compressed to the same shape and density of bricks.
Under the assumption that your feathers have not been mechanically compressed into a brick, and you have not created a total vaccum surrounding the empire state building, the bricks would land first. It all comes down to surface area and aerodynamics.

Answer 3

If the feathers are dumped, they will float gently to the ground and the bricks will land first. If the feathers are packed into a box, they'll all land at the same time.

But where are you going to get the permit to drop things off the Empire State Building?

Answer 4

The bricks will land first for there is air resistance which acts as an upward opposite force upon the feathers making them land last. In a vacuum with no air they would land at exactly the same time of 9.8 m/s.

Answer 5

160 oz = 10lbs. You didn't say if they were dropped at the same time. Nonetheless feathers have a much higher resistance to air than bricks. So obviously bricks would land first if they were dropped at the same time. In vacuum they would land together. I don't really know why you asked this question.

Answer 6

Everyone is making refence to the weights being equal. This really doesn't matter. If you look at your position equation:

s(t)= 1/2 a t^2 + vo t + so

No where do you see mass. What you do see is acceleration. Normally acceleration is g or -32ft/s^2 or -9.815 m/s^2 but it is fair to say that a will not equal g for anyone who has ever dropped a feather therefore we can safely say that the bricks would land faster.

Answer 7

Well if you make the rocks and feathers land on the authorities heads, you dont have to worry about them otherwise, 15 mins tops.

Answer 8

if 16 oz = 1 lbs, then both have a weight of 10 pounds and will fall at approximatly the same velocity.