00:01
And this problem we have a knight that is trying to exit in castle over a drawbridge, but the drawbridge hasn't been lowered all the way.
00:14
So what we have here is we have the castle here, and we have the drawbridge here.
00:21
The knight and his horse are at the end here, a distance of d away, or one meter, away from.
00:30
The end.
00:32
The chain that would raise and lower the draw bridge is here and it is at a distance x or 3 meters from the end of the bridge.
00:44
The bridge itself weighs or has a mass of 2 ,000 kilograms and the horse and the knight have a mass of 1 ,000 kilograms.
00:57
They also give us this distance h but i don't think we ever need to use that really but that's 12 meters and the length of the bridge itself is 8 meters so they want to think they want us to first determine let's see here what is they asked for the first determine the tension in the cable and the horizontal and vertical force components acting on the bridge at the hinge okay so we want to know this and we want to know these guys so the first thing we can do to find the tension in the cable is take moments of about this point here, the pivot point, because then these forces act through that point and will not show up in our moment balance.
01:41
So we have the moment due to the tension, okay? so this distance here is l minus x and that's perpendicular to the tension, so we have just have t times l minus x and that's in the counterclockwise direction.
02:01
The, let's see here, the moment caused by the weight of the rider and the horse, we can, again, we can look at it either as a component, this component of the force, or use this moment arm...