What is an imput force, output force, and fulcrum, and how are they used in the body?

Question: I am really confused with these and no matter what i read i just can't understand what they are, and how they are used in the body. Thank You!

Answer: What you are asking about is lever systems where you can use a force of one size to exert a force of a different size (usually used so you can use a small force to do a job that requires a large force). Here's a small experiment to demonstrate: open a door fully then place your hand near the side of the the door away from the hinge and push it shut. Now do it again but with your hand at the side close to the hinge - you should feel that it was more difficult. This is because the door acts as a lever - it magnifies the effect of the force we put in by moving it away from the turning point (in this case the side with the hinges) so we don't need to use as big a force. Now you have a bit of background I can answer your question. The fulcrum is the point around which your lever turns. This point doesn't move. The input force is the force you have to put in, and the output force is the force you get out. For example, a wheelbarrow works on a lever system. The centre of the wheel is the fulcrum, the force you lift the handles with is the input force, and the weight of the items in the wheelbarrow is the output force. By using a lever in this case we can lift things that are normally too heavy for us to lift. An example of a lever in the body is in our arms. Our elbow acts as the fulcrum, and your bicep inputs a force to lift your lower arm. You may be holding something in your hand, and the weight of this will be your output force. By using a lever, our body can lift items which have a larger weight than the size of force our biceps could exert.

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