M3 (Edexcel): Kinematics Watch

alex_hk90
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#1
Report Thread starter 10 years ago
#1
Here's the question I'm having trouble with:
a = 3 \sqrt{x}
When t = 0, v = 0 and x = 0
Show that x = \frac{1}{16}t^4
I just can't see where the t comes from.
Thanks in advance for any help.
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xx-footy-fan-xx
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a= d/dx(0.5v^2) = 3x^0.5
intergrate, then rearrange to get v as the subject.
then u know that v = dx/dt, so put all the terms containing x on one side and t on the other side. then integrate and then u need to rearrange it to get it in the form u want.

hope that helps
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div curl F = 0
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Hi,

Well  a = \frac{dv}{dt} = \frac{dv}{dx} \frac{dx}{dt} = v \frac{dv}{dx} = 3 x^{\frac{1}{2}}

so integrating them up gives an expression like:  v(x) = \frac{dx}{dt}

so if you integrate them up again you'll get the answer you posted (just worked it through myself)
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alex_hk90
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#4
Report Thread starter 10 years ago
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Thank you. :tsr2:

I thought that was the way to do it but was doing the second integration wrong.
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