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Seed 71

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course Phy 121

A ball falls freely from rest at a height of 2 meters. Observations

indicate that the ball reaches the ground in .64 seconds. •Based on

this information what is its acceleration?

answer/question/discussion:

v0 = 0m/s

`ds = 2m

`dt = .64s

`ds/`dt = vAve = 2m/.64s = 3.125m/s

Vf = 6.25m/s

Vf^2 = v0^2 +2a`ds

A = (vf^2 – v0^2) / 2`ds

A = (6.25m/s)^2 / 2(2m)

A = 39m^2/s^2 / 4m

A = 9.75m/s/s

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• Is this consistent with an observation which concludes that a

ball dropped from a height of 5 meters reaches the ground in 1.05

seconds?

answer/question/discussion:

????not sure how to do this one?

@&

You are given `ds and `dt for the vertical motion, and you know that v0 = 0. So this question is answered in a manner identical to the preceding.

*@

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• Are these observations consistent with the accepted value of

the acceleration of gravity, which is 9.8 m / s^2?

answer/question/discussion:

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Self-critique (if necessary):

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Self-critique rating:

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