- #1

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How long will it take to reach the desired spin rate?

**Formulas:**

T = rFsinTHETA

T = I {alpha}

I = MR^2

**Finding anuglar acceleration:**

2RF = MR^2 {alpha}

2F = MR {alpha}

2F/MR = {alpha}

**Finding the desired spin rate:**

a = v^2/r

= w^2r^2 / r

= w^2r

w = sqrt(a/r)

= sqrt(g/r)

**Finding the time:**

t = w/ {alpha}

= sqrt(g/r) * MR / 2F

= sqrt(9.81 / 23) * (7.9*10^5) * (23) / (2 * 150)

= 3.96 * 10^4

Mastering Physics says I am wrong. Where is the mistake?