Hello this is Tom for every step physics dot com I’m gonna do actual test problem number seven on the sheet here which I’ll show you the problem and let’s get started you go to my main menu and because you know it’s a collision problem our momentum problem you’re going to scroll down to a collision
if you didn’t know it was that you and you thought it was momentum you would go to momentum and it’d take you to the same spot but and this one here decides certain words in a problem to see whether it’s a momentum problem or a collision problem in this case number seven says is what releases scroll down to that thing that separates momentum problems from collision problems that the two masses are at rest at the beginning so they can’t collide so just a little information there
and we’re gonna find the bullets final velocities so we’re join to choose final velocity of mass 2 we’re gonna enter mass 1 which is you have to press Alpha before you enter anything in my programs Alpha 120 and it says gram so we’re gonna choose grams a show you how to convert that put that on your paper and
the bullets mass is 5 grams does a quick conversion and the releasing velocity is alpha .5 meters per second and because we’re releasing or pushing you have to you push off to the left if you were it was happening in reality and you push to the right so our velocity is gonna go to the left which is number two
becomes a minus and I check and see if tell you show you so that you can see if you’ve entered the right stuff or if you are happy with it I say it’s okay and momentum is p1 is the momentum of mass one which is the gun and the puck an that’s the mass times the velocity so it’s minus .06 kilograms per meters per second and because one of the rules in physics P one plus p2 equals zero we have the p1 is minus .06 so that becomes a a positive number for p2 because they’re equal and then we can figure the final velocity
of the bullet which is 12 meters per second pretty neat huh, every step physics dot com
This is a video from every step physics dot com
demonstrating how my program work on the TI-89 Titanium calculator
and other calculators in the TI system for physics and calculus problems
here’s a problem that is on many tests in physics
and ah if a bullet traveling at three hunderd fifty
meters per second strikes a steel plate
at an angle of 30 degrees as shown It recochets off
with the same angle at a speed of three hundred twenty meters
per second what is the magnitude of the impulse that
the plate gives the bullet
and in my programs ah you
find first what the problem is asking in this case it’s asking impulse
and you go to my menu and you scroll down for impulse
and then you on the side of your problem
instead of looking at it or thinking about the problem at all you just
put what’s given here which is mass
twenty grams and initial velocity
which is three hundred fifty meters per second final velocity would be
three hundred twenty meters per second and then a thirty degree angle
and here’s the picture of what’s happening and this is really vector addition
so let’s get started here ah you have to press second alpha
to put these letters in here to get to my program menu
p h y s i c s and then you have to press alpha again
to put the open and closed parenthesis and press enter and you are into my menu
I’ve scrolled down to impulse here to save some time
but you start it brings you to the top of the menu
and then you have all these other choices and uhm
we get to impulse we press enter
gives you these variables here for impulse
and right now in this problem we want the mass
the initial velocity the final velocity
and the angle we choose that
we enter your variables you have to press alpha first
before we enter any variables into the entry lines of my programs
so were going to press alpha and put down
put in twenty it also might give you kilograms or grams
in this case it gives you the bullet as grams so I’m going to put that there
it shows you you take twent and divide it by a thousand
to get point zero two kilograms which is necessary for the formula
and the initial velocity your going to press alpha
and put in three fifty that’s the way the bullet is traveling
and it’s not in centimeters it’s in meters
so were going to choose number two you can press or scroll to that choice
final velocity alpha three twenty
meters again per second and then the angle is
alpha thirty I always show you what you’ve entered
so you can change it this looks good to me
it’s been changed from grams to kilograms etcetera
and this is vector addition who would have known that
if you just saw a problem in a test ah here’s the impulse vector resultant
ah the square root of the x axis and y axis
and the I of the impulse and here’s the formula
and then we add the the all the variables
you write this on paper you don’t think about it
and the I y is six point seven newtons second
and the answer is six point seven two three one
newtons second pretty neat huh
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