welcome to electr on line now let's take a look at our Square Threaded Screw in the case where we have pending motion downward now there's two different cases that you can encounter one where the angle f is larger than the angle Theta the angle Fe is the angle between the reactionary force and the normal caused by the coefficient of friction Theta is the what we call the lead angle the angle made by the thread so if the angle Fe caused by the coefficient of friction is larger than the lead angle then we have a case here where f is larger than Theta and that's what we're talking about here in the next video we'll switch things around and we'll call the angle F smaller than the angle Theta to see what happens on the the case where we have pending motion downward now notice the force is applied in the opposite direction so this is now in a clockwise direction there's the moment arm of the applied force and therefore we can say that the force acting on the thread can be found by taking the ratio of the moment arm to the the average radius of the thread now notice that the reactionary force is in the opposite direction now now we're trying to apply a force this way so the the force is trying to push the thread downward that's what we're trying to do here we're trying to push the screw downward of course we have the weight helping us down helping the screw down and then we have the force of supplied helping the screw down so you'll need less as of force in order to do that also notice that the angle here between the vertical the weight and the reactionary force is now F minus Theta which is a smaller angle than what we had in the previous video a smaller angle here means that we need a smaller force in order to get the screw down that's another way of looking at it and so that would be the case in which we're trying to get the screw to go downward both with the help of the weight of the screw and the force applied at at the end of the handle there and that's what the sum of the forces will look like in the case that the angle F caused by the friction force is larger than the angle Theta which is the lead angle of the screw and that's how it's done