Classification of Levers (Andrew Salg)

Classification of Levers

Principle Investigated: Bones used as levers in the human body along with muscles to perform from simple to complex movements.

Standards : Physical Education Content Standard 1.Students demonstrate knowledge of and competency in motor skills, movement patterns, and strategies essential to perform a variety of physical activities.

1.2 Identify the characteristics and critical elements of a highly skilled performance in individual and dual activities and demonstrate them.

Materials: 2.37 lbs. weight, pen or pencil, and a uninjured body

Procedure:

First the students will open a spread sheet where they can put their responses.The first type of lever the class that will be discussed will be the first class lever. Students will start with their head tilted their towards their chest. The students will then slowly raise their head to them looking straight forward. As an extra the students can also tilt their head back looking up at the ceiling, and then slowly bring their head down to look straight forward.

2.Next the students will take the weight that was distributed to their group and perform a third class lever movement. A student will take the weight in their hand and perform a bicep curl. The motion includes having their palm with the mass facing them, and then pulling the weight towards with their forearm. Finally slowly lower the weight to the resting position with their arm at their side. This shows the arm as a third class lever.

3.Finally is the second class lever, currently there is still a debate in some sports science circles about second class levers in the body. Some do not believe that there are any present, but other suggest calf raises are an example of a second class lever movement. A calf raise is performed by standing on either one or two legs, and then pushing straight up into the air using the balls of the feet. Students can use the table or another person for support if they want to,

Student prior knowledge: The students should have brief knowledge in eccentric force. Eccentric force is a force that is not in line with the center of gravity of a freely moving object (throwing a football). Also torque along with the summation of torques.Torque is the turning effect in a eccentric force, and summation of torques is when two or more torques work together to perform a movement like the obliques rotating the trunk of a person. Next vector, a vector is a measure of quantities that will factor in magnitude and direction of an object. An example of this is a car traveling 35 mph in westerly direction.

Finally understanding speed is related distance and velocity relates to the direction of movement while factoring in speed.

Explanation: To better explain how bones acts as levers and how muscles help perform movement we use the principle of levers. This applies to a person performing movement we have to look at the following equation E x EA= R x RA. E represents effort, and EA means effort arm. R represents resistance, with RA meaning resistance arm. The equation states that when both sides of the equation have the same amount of force, it creates equilibrium causing movement. However if one side has greater force than the other it results in movement of the lever.

The equation shows the importance of lever or arm length. if the EA is increased and RA remains constant the amount of effort will decrease to achieve balance. Furthermore when the EA is longer pertaining to first class or second class levers the lever will favor force. However it will come at a cost of speed and range of movement. If the RA is increased the effort of the muscle increases. When a RA is longer than the EA with first or third class levers, the lever will favor speed and distance.

The demonstration is meant to be a hands on experience with science. Having kinesthetic activities It combines health science with physics in a high school setting. The lesson reinforces the knowledge from learning the name of bones and muscles, but will introduce them to new terms and their definitions fulcrum, velocity, etc.

Questions & Answers:

1. What are some of the factors to consider when looking at levers?

Some of the factors to consider when talking about levers is the length of the lever. Arm length can provide a greater amount of force, but it will come at the expense of expending more energy. Also to consider is amount and strength connections are on a lever. This is based off area of a surface giving a better opportunity for connections to be made. A bone with a larger surface allows for more muscle fibers to be placed on it giving increasing power. Some levers will provide more force to an object, or put more speed and distance to an object.

2. What would happen if the EA(effort arm) the RA(resistance arm) are equal in force? Explain your answer.

A. The effort arm and the resistance arm would balance the weight placed on the lever. This is because the vector line (starting at the site of resistance) will be perpendicular in distance to the axis or fulcrum. The effort will also be perpendicular in distance to the fulcrum as well, giving the lever ability to balance. Now if either one changed the result will be more energy towards one arm resulting in movement.

3.Decide which lever(s) is being used in the following situation. A student picks up a box from the ground, and take it to his room. First he must push open a door to get to his room. He manages to balance the box by putting it on his left leg. He manages to push the door. He then places the box on his room's bottom shelf.

A. The first lever being used in the situation is a third class lever. By picking up the box the effort is placed on his biceps, and the resistance is coming from the box. Second is a first class lever because the student is balancing a box. The effort is coming from the gravity pulling the box down, and the resistance is pulling down on the other side, with the axis in the middle. Next lever is a second class lever when he pushes open his door. The effort is coming from the forearm to open the door, and the resistance is right below the elbow where the axis is located. The final movement is a third class lever. The student is lowering the box onto the shelf forcing his biceps to exert effort, with his elbow as the axis, and the box and gravity as resistance.

Applications to Everyday Life: One application is performing movements during the day. Throwing a baseball for example. The arm is acting as a third class lever with the ball, and the pitchers hand is created torque before the balls release.

Balancing a pencil or any object on a person's hand acts like a first class lever. The finger is the axis, gravity as the effort, and mass on the other side acts as resistance.

We can even go to a construction site to view heavy machinery like a back hoe that relies on hydraulics and steel instead of muscles and bone. The machine uses first class when digging into soil. The arm of the machine has effort by the proximal lever, followed by the axis, and then finally the resistance is the distal lever It becomes a second class lever when the arm is extended and trying to push an object like a rock across a surface. .

Videos:

Here is a seesaw acting as a first class lever.

Here is an example of a third class lever

How to make your own weights.http://www.ehow.com/how_8173410_make-own-hand-weights.html or you could buy them at any sports outlet http://www.sportchalet.com/

Page updated

Google Sites

Report abuse