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## Homework Statement

The two blocks in the figure (Intro 1 figure) are connected by a massless rope that passes over a pulley. The pulley is 17 cm in diameter and has a mass of 2.0 kg. As the pulley turns, friction at the axle exerts a torque of magnitude 0.46 Nm .

If the blocks are released from rest, how long does it take the 4.0 kg block to reach the floor?

(Intro 1 Figure):http://session.masteringphysics.com/problemAsset/1070551/3/12.P70.jpg

## Homework Equations

torque= r * F

sum of torques = moment of inertia * angular acceleartion

angular acceleration * radius = acceleration

x=v0t + 1/2 a t^2

## The Attempt at a Solution

I now that v0 is o so the i solve for t in the equation, t = sqrt(2h / a).

a = [ F / r + (m1 - m2)g ] / (m1 + m2 + m3 / 2)

then i plug in a into t=sqrt(2h/a)

= sqrt{ h(2m1 + 2m2 + m3) / [ F / r + (m1 - m2)g ] }

=t = sqrt{ 1( 2 * 4 + 2 * 2 + 2) / [ 0.46 / 0.17 + (4 - 2)9.81 ] }

=.79s

I got it wrong, can anyone help me to see what i did wrong.