Impulse and momentum dodgeball example (video) | Khan Academy
Source: B. Karlsen. unions invisible or problematizing interracial relationships as part of a deviant world. starring the Cuban-born Desi Arnaz and his real-life white wife Lucille Ball. as The Jeffersons, Benson, Webster, Diff rent Strokes, and Gimme a Break !. how to solve for the impulse and force applied during a dodgeball collision using the.
So if you need a way, a pneumonic device, to remember this, Jape Fat is a way to remember how impulse, change in momentum, force, and time, are all related. So let's do it.
We can't use force because we don't know it yet, but I can figure out the change in momentum 'cause I know the velocities. So, we know that the change in momentum is gonna be P final, the final momentum, minus the initial momentum. What's my final momentum? My final momentum is M times V, so it's gonna be mass times V final, minus mass times V initial, and my mass is. My final velocity is five, because the ball recoiled to the right with positive five. Positive five 'cause it's moving to the right.
I'm gonna assume rightward is positive. Then minus, the mass is. My initial velocity is not This is 10 meters per second to the left, and momentum is a vector, it has direction, so you have to be careful with negative signs here. This is the most common mistake. People just plug in positive 10, then get the wrong answer. But this ball changed directions, so the two velocities here have to have two different sides, so this has to be a negative 10 meters per second, if I'm assuming rightward is positive.
This leftward velocity, and this leftward initial velocity, has to be negative And, if you didn't plug that in, you'd get a different answer, so you gotta be careful. So, what do I get here if I multiply this all out?
I'm gonna get zero, no, sorry, I'm gonna get one kilogram meters per second, minus a negative two kilogram meters per second, and that's gonna give me positive three kilogram meters per second is the impulse, and that should make sense.
The impulse was positive. The direction of the impulse, which is a vector, is the same direction as the direction of the force. So, which way did our face exert a force on the ball?
Our face exerted a force on the ball to the right. That's why the impulse on the ball is to the right. The impulse on this person's face is to the left, but the impulse on the ball is to the right, because the ball was initially going left and it had a force on it to the right that made it recoil and bounce back to the right. That's why this impulse has a positive direction to it. Now, if you've been paying attention, you might be like, wait a minute, hold on.
What we really did was we found the change in momentum of the ball, and when we do that, what we're finding is the net impulse on the ball. In other words, the impulse from all forces on the ball. But what this question was asking for was the impulse from a single force. The impulse from just the person's face.
Now, aren't there other forces on this ball? Isn't there a force of gravity? And if there is, doesn't that mean what we really found here wasn't the impulse from just our face, but the impulse from the person's face and the force of gravity during this time period?
And the answer is no, not really, for a few reasons. Most important reason being that, what I gave you up here was the initial horizontal velocity. This 10 meters per second was in the X direction, and this five meters per second, I'm assuming is also in the X direction. When I do that, I'm finding the net impulse in the X direction, and there was only one X directed force during this time and that was our face on the ball, pushing it to the right. There was a force of gravity.
That force of gravity was downward. But what that force of gravity does, it doesn't add or subtract any impulse in the X direction. It tries to add impulse in the downward direction, in the Y direction, so it tries to add vertical component of velocity downward, and so we're not even considering that over here. We're just gonna consider that we're lookin' at the horizontal components of velocity. How much velocity does it add vertically, gravity?
Typically, not much during the situation, because the time period during which this collision acted is very small and the weight of this ball, compared to the force that our face is acting on the ball with, the weight is typically much smaller than this collision force.
So that's why, in these collision problems, we typically ignore the force of gravity. So, we don't have to worry about that here. That's not actually posing much of a problem. We did find the net impulse in the X direction since our face was the only X directed force, this had to be the impulse our face exerted on the ball.
Now, let's solve one more problem. Let's say we wanted to know: Now take the diff rings out of the outdrives, and feel the diff rings with your fingernail to see if there is a small ridge that the diff balls have created.
If there is a small ridge, flip the diff rings over to the smooth un-used side, if both sides have been used it is time to replace the diff rings. Now take some grit sandpaper and sand the diff rings in a circular pattern, until there is no shine or ridge on the diff rings. Most diff rings come too polished and cause the diff to slip because the balls have nothing to grab on to.
Many diff rings also have minor imperfections, and are not completely flat. Sanding fixes both of these problems. You need only to sand the side facing the diff balls, however sanding both sides does no harm. Building the Diff Now it is time to build the diff. Make sure all the parts are clean and free of debris, grit, and dirt.
Now set the diff rings on the outdrives. Apply Diff Lube onto the top of the diff rings, being more generous this time.
Impulse and momentum dodgeball example
Now place the diff gear onto the left outdrive[the outdrive with the nipple]. Apply more Diff Lube to the holes in the gear and place the diff balls in the holes. It is important to make sure no debris gets into the diff, so be careful.
Now set the outdrives aside and we will look at the thrust bearing assembly. If you are re-using your thrust washers check to make sure there is no ridge on the washers that the thrust balls have created.
If there is flip them over to the smooth, un-used side. If both sides have been used it's time to replace the thrust washers. Next set the six thrust balls onto the top side of the washer, and apply a little more Black Grease on top of these. Slide the second washer on top of the diff balls, then slide the bolt up into the right outdrive[outdrive without nipple]. Now install the diff bearings into the diff by sliding them into the slot on the right outdrive.
Apply a little more Diff Lube onto the right outdrive, and slide both outdrives together, and set aside for a moment. Now find your diff thrust spring and t-nut. Please note that if it is a new diff thrust spring you will need to compress it first, with a pair of pliers. Slide the thrust spring into the left outdrive, followed by the t-nut. Make sure the t-nut is facing the right direction, and has the tabs on the top, not the bottom.
What is conservation of momentum? (article) | Khan Academy
Slowly tighten the diff, making sure the t-nut is compressing the thrust spring. Only tighten the diff enough to when you can not move the diff gear while holding both outdrives. Before reassembling the transmission clean out all of the old grease in the transmission gears with motor cleaner spray, and apply a couple of drops of 50wt shock oil to get a quite, smooth transmission. Now reassemble the transmission and the rear end of the buggy by reversing the steps you took in disassembly.
Setting the Diff This next part can be confusing, so you might want to read thru it before continuing. With your car back together you can now set the diff.
First, you will need to tighten your slipper clutch all the way down. Next hold the spur gear and the right wheel with your right hand and try to turn the left wheel with your left hand. You are trying to get the diff as loose as you can without it slipping, and as tight as it can without binding. Now that you have set your diff, we can break it in. Before you do this loosen your slipper clutch back to normal. Breaking-In the Diff Breaking in the diff is important and you will have a much smoother diff after this is done.
To break in the diff hold one tire and give the car a small amount of throttle for about seconds, then change sides and hold the opposite tire.