Physics
posted by Tammy .
The position of a toy locomotive mobing on a straight track along the xaxis is given the equation x=t^36t^2 +9t where x is in metters and t is in seconds. The net force on the locomotive is equal to zero when t is eqaul to
a) zero
b)2 s
c)3 s
d)4s
e)5s
Would the answer be b)2 s? I found the double derivative of the equation and set x to 0 and solved for t.
f'= 3t^2  12t + 9
f"=6t  12
yes, t=2
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