Khan/khan-exercises — Issue #15153: Kinematic equations - Rounding the answer too soon
Author: KhanBugz
Created: 2012-03-01 17:58:22+00:00
State: open
Labels: ie8, wrong-or-unclear, xp

v 2 f =v 2 i +2ad v_f^2 = v_i^2 + 2ad

±v 2 f −2ad − − − − − − − √ =v i \pm\sqrt{v_f^2 - 2ad} = v_i

±(−5.76m s ) 2 −2(−9.8m s 2 )(31.74m) − − − − − − − − − − − − − − − − − − − − − − − − − − √ =v i \pm\sqrt{(-5.76 \frac{\text{m}}{\text{s}})^2 - 2(-9.8 \frac{\text{m}}{\text{s}^2})(31.74 \text{m})} = v_i

while solving for vi here, the result was rounded way before the answer, so instead of getting 24.27m/s it gives 25.6 m/s

[kinematic_equations.html?seed=27&problem=freefall](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/kinematic_equations.html?seed=27&problem=freefall&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/kinematic_equations.html?seed=27&problem=freefall&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5B%5B%5C%2224.27%5C%22%2C%5C%22m%2Fs%5C%22%5D%5D%22%2C298%5D%2C%5B%22hint-activity%22%2C%220%22%2C5%5D%2C%5B%22hint-activity%22%2C%220%22%2C5%5D%2C%5B%22hint-activity%22%2C%220%22%2C8%5D%2C%5B%22hint-activity%22%2C%220%22%2C15%5D%2C%5B%22hint-activity%22%2C%220%22%2C21%5D%5D)

[[["24.27","m/s"]]]

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