9.1 angular velocity and acceleration.pptVIP

Why things fall over Every object has a special point called the center of gravity (CG). The CG is usually right smack in the center of the object. if the center of gravity is supported, the object will not fall over. You generally want a running back with a low CG? then it’s harder to knock him down. The lower the CG the more stable an object is. stable ? not easy to knock over! Condition for stability If the CG is above the edge, the object will not fall CG when does it fall over? CG CG STABLE NOT STABLE If the vertical line extending down from the CG is inside the edge the object will return to its upright position ? the torque due to gravity brings it back. Stable and Unstable stable unstable torque due to gravity pulls object back torque due to gravity pulls object down Stable structures Structures are wider at their base to lower their center of gravity If the center of gravity is supported, the blocks do not fall over Playing with your blocks CG Object with low CG Stay low to the ground! 300 lb fullback who is 4 ft, 10 inches tall and runs a 4-40 As more and more stuff is loaded into a semi, its center of gravity moves upward. It could be susceptible to tipping over. High Profile Vehicles wind The shape of an object determines how easy or hard it is to spin For objects of the same mass, the longer one is tougher to spin ? takes more torque Hinge It matters where the hinge is The stick with the hinge at the end takes 4 times more torque to get it spinning than the stick with the hinge in the center. Rotational Inertia (moment of inertia) Rotational inertia is a parameter that is used to quantify how much torque it takes to get a particular object rotating it depends not only on the mass of the object, but where the mass is relative to the hinge or axis of rotation the rotational inertia is bigger, if more mass is located farther from the axis. How fast does it spin? For spinning or rotational motion, the rotational inertia of an object plays the same role