2. Rotational Inertia Newton’s Second Law for Rotation Rotational Inertia (Moment of Inertia) ( I ) – The slope of a graph of torque vs. angular acceleration. – The tendency of an object to continue in its same state of rotation. –A measure of an object’s resistance to changes in its rotation. –How difficult it is to start or stop the rotation of an object.

3. The blue Inertia Wand is much harder to twist! Rotational Inertia Consider the blue and red Inertia Wands. They have the same mass. Shake them up and down to confirm. Now twist them side to side. Why!

4. Notice that the units of the rotational inertia ( kgm 2 ) also indicate that it depends on the mass and the distance the mass is from the axis of rotation. Purpose:To create graphical and mathematical representations of the relationship between the rotational inertia ( I ), the total mass ( m ), and the distance the masses are from the axis of rotation ( r ) for a system of particles consisting of two point masses. Rotational Inertia of Point Masses Lab The rotational inertia depends on the mass and on where that mass is!

5. Rotational Inertia of Point Masses Lab The clamp-on Super Pulley must be adjusted at an angle, so that the thread runs in a line tangent to the point where it leaves the 3-step Pulley and straight down the middle of the groove on the clamp-on Super Pulley (Figure 1.2).

6. Rotational Inertia of Point Masses Lab Since the masses are accelerating downward. Since the string doesn’t slip, the linear acceleration of the masses is equal to the tangential acceleration of the outside of the pulley.

7. Rotational Inertia of Point Masses Lab Newton’s Second Law Experimental Rotational Inertia