Phys 1053 Notecard Questions

No= tecard Q= uestions & Answers These answers are longer than th= ose I expect from you. I will try= to clarify points of confusion that come up in your answers as well as explaining why the answer is the answer.
1	Imagine ta= king 2 friends golfing with 3 different “balls.” Adam has a small round rock, Bre= nda has a golf ball and you have a ping-pong ball. Which ball has the most inertia?=
Inertia expresses the resistance of an object to changes in its velocity. The inertial of an object is related to its mass. If the rock is assumed to be abo= ut the size of a golf ball, then it is likely to be more massive than a golf bal= l, and certainly more massive than a ping-pong ball, and therefore the rock has the greatest inertia.<= /p>
2	If each of= you now hit your balls with the same amount of force for the same amount of t= ime, which ball will leave the club head with the greatest velocity? Explain.
Newton says that F =3D ma. All the forces (F) are the same,= but the masses are different, so the accelerations (a, the change of velocity= … from zero here) will be inversely proportional to the masses; the most massive will accelerate the least and the ball with the smallest inertia = will change its velocity the most, leaving the club with the greatest speed. Therefore, we expect the ping-pong ball to have the grea= test speed when the balls first separate from the club. Of course, as the three balls no= w fly through the air, air resistance becomes a significant backwards force on = them and they will accelerate in inverse proportion to their masses again. This time, though, the accelerat= ion is negative (a.k.a. “deceleration”) and so the object with the largest mass will slow down the least, while the object with the smallest mass will slow down the most. So even though the ping-pong ball starts out with the largest velocity becau= se it was easy to accelerate, it also slows down the fastest due to the forc= e of air resistance and thus won’t travel very far before it lands. (Golf balls are designed with two issues in mind = to make them travel farther and straighter than your average small rock. First, they are designed to be a little more “bouncy” than a rock so that most of the energy y= ou impart with the club goes into accelerating the ball rather than dissipat= ing into the air/tee/club/etc. Second, they have little dimples all over the surface in order to reduce the drag effect of air resistance. So if the question were “w= hich ball is likely to go the farthest?” the answer would certainly be t= he golf ball, but that wasn’t the question!)