(SF) Simple Machines Lesson

Simple Machines

Simple machines are devices that help us do work more easily and more efficiently. You are probably not aware, but you use simple machines all of the time. When you ride your bicycle, turn a doorknob, or walk to your class, you are using some type of simple machine. Your body itself contains simple machines. Your arms and legs act as levers allowing your muscles to move your skeleton so that you can do the activities that you perform every day. Other simple machines are used by people to carry out tasks, such as jacking up a car, changing a flat tire, peeling an apple, or picking up a large load with less force. Simple machines work by giving us mechanical advantage where we can use a small force on one end to create a large force on the other. When two or more simple machines are used together, the result is a compound machine that can perform several functions at once. These machines are very common and chances are you have used more than one today.

Simple machines are used in sporting events as well. Simple machines make shots easier, cause the ball to fly further, and allow for greater speed and agility. When we watch a sporting event, we probably don't think about simple machines. Even though they are part of every sport, they go unnoticed because we do not know what we are looking for. From the baseball bat, to the hockey stick, to the tennis racket, simple machines are very much a part of sporting events. Let's look at several simple machines and see how they are related to our favorite sport. 

Lever

A lever is a stiff bar that rests on a support, called a fulcrum, which lifts or moves loads. We see levers used in sporting events more than any other type of simple machine. The bones in our arms and legs act as levers when we move, and we can use these to operate other levers used in sports. The baseball bat, the tennis racket and a hockey stick are all examples of levers that are used in sporting events. This simple machine relies on a long bar and a hinge point that allows us to gain mechanical advantage to make movements easier. Levers come in three classes; each class is characterized by where the fulcrum is located. Baseball bats and hockey sticks are both third class levers. These levers use the back hand as a fulcrum and the front hand as the force generator. A football player also acts as a lever when he makes a tackle. He positions his body in a low position so that he can lift the player with the ball and put him on the ground. Levers give an athlete a mechanical advantage where they can propel the ball or the puck forward at a high rate of speed and hit a home run or a center ice slap shot for the win.

Pulley

A pulley is a fixed wheel that pivots around a central axle. A single pulley does not provide mechanical advantage; it only changes the direction of a force. This allows a person to move things in one direction, and produce a movement in the other direction. If more than one pulley is placed in a sequence, then mechanical advantage can be gained. This system of using pulleys is called a block and tackle. The number of times the rope is looped around the pulley determines the mechanical advantage. In sports, pulleys are used behind the scenes when athletes are preparing for their event. During training, athletes use machine weights to help them achieve their physical goals. These machines are usually based on a pulley system. The athlete pulls a wire cable in one direction, and the weight is directed in the opposite direction. Pulleys are useful in exercise and training, and athletes depend on these simple machines to get them into shape for their athletic event.

Wheel and Axle

In various sports, wheel and axle simple machines are an integral part of the athletic event. Cycling, for instance, uses a combination of wheel and axles to build a human powered machine. The competition requires energy to be input by the cyclist, and the output that results propels the machine that they ride forward. This application uses a lever, as well as a wheel and axle, to provide the force necessary to propel the cyclist past the finish line. Other sports use wheel and axles, such as NASCAR, skating, and motocross, where machines are used in competition that contain one or more wheel and axle. 

Inclined Plane

An inclined plane is basically a ramp. We are all familiar with ramps that are used to load trucks, allow handicapped persons to enter a store, along with many other applications. Ramps are used in sporting events to propel riders into the air during BMX and motocross events. Ramps are also used by athletes to enter a field from a locker room or to aid fans to the upper deck at a stadium.

Screw

A screw is a modified inclined plane that wraps around a central shaft. Screws are useful to hold materials together, or to allow a gentle slope to be achieved to move materials or people in a vertical direction. Typically, screws are threaded in a right hand direction where the screw is tightened to the right and loosened by turning it to the left (you may be familiar with the saying, "Righty Tighty, Lefty Loosey"). In sports, screws are used to hold machines together that are used in competition. NASCAR, BMX, and motocross all use machines that are held together with screws. Without screws, the machines used in these sports could not be manufactured and the events that use them could not occur.

Wedge

A wedge is a specialized type of inclined plane - it is actually two inclined planes placed back to back. Wedges are typically used to separate items, such as splitting a log. Another use of a wedge is to hold things together, like a door wedge that holds a door in the open position. In sports, a football team may use a wedge on a kickoff by arranging the players in a wedge shape to split apart the other team, allowing a player with the ball to move past the other team. This is a common play for the receiving team during a football game.

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