Physics 105, Fall Term, 2009
Reading: Chapters 6.1 & 6.2
Did you complete the reading assignment?
1) Momentum is the
product of an object's mass and velocity.
2) Impulse is the change in momentum of
an object when a force is applied to it over a given time.
3) Momentum and impulse have the same units,
but momentum is something an object has, whereas impulse is something done
to an object.
There is not a lot a whole lot of applications for momentum until you start
using the Law of Conservation of Momentum and collisions, which is for next
time. Here is a slightly, culturally insensitive video that helps explain the
difference between momentum and impulse and which one is most important for
trying to break stuff:
The video explains impulse as how fast momentum is transferred. Is this a
correct definition? Why or why not?
No, impulse is how the quantity of momentum that changes, not the speed that it changes. The speed that momentum changes is force.
The momentum of the guy's fist in the video is what is important to watch. Does
the mass of his fist change?
When a board is broken easily, does the velocity of his fist change a lot?
When breaking stuff with you fist, you want to have:
High initial momentum, high final momentum
High initial momentum, low final momentum
Low initial momentum, high final momentum
Low initial momentum, low final momentum
A greater impulse is is when a force is applied over a longer period of time.
When breaking stuff, do you want a large or small impulse?
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Was there anything that you didn't understand in the reading assignment?
What was confusing to you?