Where is the slope 0?
• Where is the slope positive or negative? • Where is the slope steepest or shallowest? • “Knematics” is about the description of motion. “Dynamics” is about explaining the reasons for motion. • Forces cause changes in velocitiy. • Tracking the acceleration • Define average acceleration as the rate of change of velocity (see equation). Acceleration units are m/s2. • Note: sign of acceleration can be confusing. Sometimes helpful to consider “which way is it trying to go?” • As can been seen by comparing defining equations for v and a, acceleration graph is obtained from velocity graph by “slope to value”. • Near surface of earth, all unsupported objects accelerate down at g=9.81 m/s2 (if air has little effect). That’s called “free fall.” • Constant acceleration can only result in one direction reversal. So for vibrations, even acceleration must not be constant. One could continue by defining “rate of change of acceleration,” but luckily we’ll see that we don’t have to.
