LetвЂ™s assume the values were not measured, but were chosen hypothetically, in which case they are exact numbers like in a definition and donвЂ™t affect the significant figures. The weight of the ball in the example is not written in scientific notation, so itвЂ™s not really clear if the zeros are placeholders or if they are significant. That means that the effort needs to be 8.667 times larger than the load, so for the 50 lbВ load the bicep tension would need to be 433 lbs! That may seem large, but we will find out that such forces are common in the tissues of the body! *Adjusting Significant FiguresДЇinally, we should make sure our answer has the correct significant figures. The effort arm was 1.5 inВ and the load arm was 13.0 in, so the load arm is 8.667 times longer than the effort arm. We are now ready to determine the bicep tension in our forearm problem. LetвЂ™s calculate the biceps tension need in our initial body lever example of a holding a 50 lb ball in the hand. First (top), second(middle), and third(bottom) class levers and real-world examples of each.

Third class levers have the effort in the middle. Second class levers have resistance in the middle. First class levers have the fulcrum in the middle, between the load and resistance. The lever classes are identified by the relative location of the resistance, fulcrum and effort. When the resistance is caused by the weight of an object we call it the load. Using the standard terminology of levers, the forearm is the lever, the biceps tension is the effort, the elbow joint is the fulcrum, and the ball weight is the resistance. Image Credit: Openstax University Physics The elbow joint flexed to form a 60 В° angle between the upper arm and forearm while the hand holds a 50 lb ball. For example, the forearm is a 3rd class lever because the biceps pulls on the forearm between the joint (fulcrum) and the ball (load). There are three classes of levers, and all three classes are present in the body. A lever is a rigid object used to make it easier to move a large load a short distance or a small load a large distance. One component of strength is the ability apply enough force to move, lift or hold an object with weight, also known as a load. The ability of the body to both apply and withstand forces is known as strength. To analyze forces in the body, including the effects of leverage, we must study the properties of levers. The forces required to move people are large to begin with, and the biomechanics of the body can amplify those forces by the effects of leverage, or lack thereof. Spinal load measurements indicated that all of the routine and familiar patient handling tasks tested placed the nurse in a high risk category, even when working with a patient that вЂњ only 49.5 kg and was alert, oriented, and cooperative-not an average patient.вЂќ People are inherently awkward shapes to move, especially when the patientвЂ™s bed and other medical equipment cause the nurse to adopt awkward biomechanic positions.

In fact, вЂњdisabling back injury and back pain affect 38% of nursing staffвЂќ and healthcare makes up the majority of positions in the top ten ranking for risk of back injury, primarily due to moving patients. Moving patients is a routine part of JoleneвЂ™s work as a MED floor RN, but in reality there is nothing routine about the biomechanics of lifting and transferring patients.

Type 3 lever