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# Physics A level question help watch

1. A sphere of polystyrene and a small sphere of lead, each of mass 0.20kg are released together from rest and fall down a deep well with water at the bottom. The sphere of lead is found to take 4.0s to reach the water surface.

Calculate the speed with which the lead hits the water, assuming no air resistance.
>39 m/s

What is the depth of the well to the water's surface.
>78m

The polystyrene sphere takes 6.0s longer to hit the water.

Find the upward force, assumed constant, that must be acting on the polystyrene and explain why it is reasonable to assume that the affect of this force on the lead sphere is negligible.

> ??
2. I would assume it would involve finding the acceleration of the polystyrene ball using SUVAT and the time of 10s given and then using this with F = ma and the weight of the polystyrene to find the air resistance acting on it.

For the second part, think about the surface area of each sphere.
3. (Original post by WarByte)
I would assume it would involve finding the acceleration of the polystyrene ball using SUVAT and the time of 10s given and then using this with F = ma and the weight of the polystyrene to find the air resistance acting on it.

For the second part, think about the surface area of each sphere.
Oh.. I just realised I have been using 6 seconds instead of 10. Now I know why I got it wrong. Thank you!

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