Archive for the ‘Momentum’ Category

January 13, 2014 · by physics · Acceleration, Collisions, Momentum

Popeye, of mass 70kg has just downed a can of spinach. He accelerates quickly and stops Bluto, of mass 700kg (Bluto is very dense), who is charging in at 10 m/s. What was Popeye’s speed?

a. 10 m/s
b. 31 m/s
c. 50 m/s
d. 100 m/s

Raw Transcript

Hello this is Tom from every step physics dot com going to an actual physics problem from a test final
and I’m gonna do number nine here on this sheet, I’ll show you the sheet let’s do it I’m going to scroll down to collisions and this next one in the problem it says that he stops Bluto so that word is a key one whether it’s a momentum or collision problem. Now this is a special collision problem because when it says stop that means that both of the well after they hit they stick together and stop so that means that
the final velocities are 0 for both of them so it’s a special momentum problem maybe a trick problem
a lot of trick problems in physics as if physics wasn’t hard enough and we’re gonna find what are we gonna find we’re gonna find Popeyes initial…um velocity so we’re going to choose Vi1…we’re going to enter the mass Alpha is 0:00 kilograms, you have to press alpha to enter anything into my entry lines here and Bluto is 700 kilograms initial velocity of Bluto is 10…Bluto is 10 meters per second oops, press Alpha first and he’s going to the left, Popeyes going to the right so we choose -x axes and you can see if it’s correct, which it is, you can change it if you you wanted and so the momentum of Pluto is mass times velocity which is his mass is 700 plus that which is minus 7000 kilograms meters meters per second and since one of the laws of physics is that p1 plus p2 equals zero, so we enter that in the equation and then we solve for p1 with becomes a positive 7,000 that’s what the momentum of Popeye is and so we do the calculations here we come up with 100 meters per second for Popeye which is on the test you just circle that one and get a hundred percent on problems like that, pretty neat huh? every step physics dot com.

January 6, 2014 · by physics · Bullets, Momentum, Physics Test Questions

A miniature spring-loaded, radio-controlled gun is mounted on an air puck. The gun’s bullet has a mass of 5.00 g, and the gun and puck have a combined mass of 120 g. With the system initially at rest, the radio controlled trigger releases the bullet horizontally causing the puck and empty gun to move with a speed of 0.500 m/s. What is the bullet’s speed?

a. 4.80 m/s
b. 11.5 m/s
c. 48.0 m/s
d. 12.0 m/s

 Raw Transcript

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