2. A lever consists of a rod or bar that rests and turns on a support called a fulcrum . effort resistance
3. A force of effort is applied at one end of the rod to lift a load placed at the other end. A lever can help lift a weight with less effort. effort resistance fulcrum
4. Prying something loose with a crowbar is using a lever. Some machines, such as a catapult, use a lever to hurl objects.
14. An example in the human body of a second-class lever is the Achilles tendon , pushing or pulling across the heel of the foot.
15. An example of a third-class lever in the human body is the elbow joint : when lifting a book, the elbow joint is the fulcrum across which the biceps muscle performs the work.