\(\def \u#1{\,\mathrm{#1}}\) \(\def \us#1{\,\mathrm{\scriptsize #1}}\) \(\def \abs#1{\left|#1\right|}\) \(\def \ast{*}\) \(\def \deg{^{\circ}}\) \(\def \tau{\uptau}\) \(\def \ten#1{\times 10^{#1}}\) \(\def \redcancel#1{{\color{red}\cancel{#1}}}\) \(\def \BLUE#1{{\color{blue} #1}}\) \(\def \RED#1{{\color{red} #1}}\) \(\def \PURPLE#1{{\color{purple} #1}}\) \(\def \th#1,#2{#1,\!#2}\) \(\def \lshift#1#2{\underset{\Leftarrow\atop{#2}}#1}}\) \(\def \rshift#1#2{\underset{\Rightarrow\atop{#2}}#1}}\) \(\def \dotspot{{\color{lightgray}{\circ}}}\) \(\def \ccw{\circlearrowleft}\) \(\def \cw{\circlearrowright}\)
Chapter 5: Impulse and Momentum
1.

New Perspectives

Well, that's it. We've described how things move (with velocity and acceleration) and explained why things move (with forces). We could stop now, call it a day. Except...

Well, real-life motion can be complicated. So far we've only really dealt with systems of Constant Acceleration and constant force, for one thing. But in real life, forces are usually applied over a period of time. I push a box for 10 seconds, or a baseball bat makes contact with a ball for 5 microseconds, and so forth. And that force usually changes with time, such as when a ball collides with a bat, and so the acceleration isn't constant either. Dealing with nonconstant forces and accelerations normally requires calculus, but who has time for that? Fortunately, there are other ways of looking at these problems, using the same physics but at slightly different perspectives, that can let us study these problems more easily. This chapter is about one such perspective, which is particularly useful in problems involving collisions.