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**1. The problem statement, all variables and given/known data**

Rigid rods of negligible mass lying along the y axis connect three particles (Fig. P10.20). The system rotates about the x axis with an angular speed of 2.90 rad/s.

Figure P10.20

(a) Find the moment of inertia about the x axis.

______kgm2

Find the total rotational kinetic energy evaluated from 1/2 I2.

______J

(b) Find the tangential speed of each particle.

______m/s (4.00 kg particle)

______m/s (2.00 kg particle)

______m/s (3.00 kg particle)

Find the total kinetic energy evaluated from mi vi2/2.

______J

**2. Relevant equations**

I = sum of (r^2*m)

**3. The attempt at a solution**

My teacher told us to use I = sum of (r^2 * m) i am not sure how this works if some of the r's (distances from the axis of rotation) are negative. i tried subtracting the negative ones, or just plugging them in and squaring them, thus making them positive, to no avail. Any help would be greatly appreciated! the most difficult part of this for me is the moment of inertia.

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