Basic average acceleration confusion

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SUMMARY

The discussion centers on the confusion between two kinematic equations: v = u + at and v² = u² + ad. The user correctly identifies that when applying the values v = 12 m/s, u = 0 m/s, d = 24 m, and t = 4 s, the first equation yields the correct average acceleration of 3 m/s², while the second equation incorrectly suggests 6 m/s² due to a missing factor of two. The correct form of the second equation is v² = u² + 2ad, which clarifies the discrepancy. Understanding when to use each equation is crucial for accurate problem-solving in physics.

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seagull
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Hi there,

I'm struggling to distinguish why the following two equations are giving distinct answers, when the question explicitly states either could be used:

v=u+at
v^2=u^2+ad

when
v=12 m/s
u=0 m/s
a (average acceleration)= the unknown variable
d=24 m
t=4s

Theoretically, the two should provide the same answer; however, only the former is providing the correct answer (3 m/s^-2), the latter is giving 6 m/s^-2 as the answer. If this is the case, how do I recognise which equation is ideal for the problem in question. If I'm making some clearly idiotic mathematical error, I'm sorry, haha!

Cheers!
 
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seagull said:
v^2=u^2+ad
There is a factor of two missing here, it should be
$$v^{2}=u^{2}+2ad$$
 
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