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| the branch of physics dealing w/ the study of forces and the motion produced by their actions |
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| involves taking the principles and methods of mechanics and applying them to the structure and function of the human body |
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| deals w/ factors associated w/ nonmoving or nearly nonmoving systems |
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| involves factors associated w/ moving systems and can be divided into kinetics and kinematics |
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| deals w/ forces causing movement in a system |
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| involves the time, space, and mass aspects of a moving system |
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| focuses on the manner in which bones move in space w/o regard to the movement of joint surface, such as shoulder flexion/extension |
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| deals w/ the manner in which adjoining surfaces move in relation to each other- that is, in the same or opposite direction |
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| a quantity having both magnitude and direction |
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| a vector that describes speed and is measured in units such as feet per second or miles per hour |
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| a quantity that describes only magnitude (e.g., length, are, volume, & mass) |
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| refers to the amount of matter that a body contains |
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| the property of matter that causes it to resist any change of its motion in either speed or direction |
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| the tendency of force to produce rotation around an axis (motions w/in the body produce motion around joint axes) |
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| a force developed by two surfaces, which tends to prevent motion of one surface across another |
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| Newton's First Law: Law of Inertia |
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| Newton's Law which states: that an object at rest tends to stay at rest, and an object in motion tends to stay in motion |
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| any change in the velocity of an object (whether it is slowing down or speeding up) |
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| Newton's Second Law of Motion: Law of Acceleration |
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| Newton's Law which states: the amount of acceleration depends on the strength of the force applied to an object |
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| Newton's Third Law of Motion: Law of action-reaction |
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| Newton's Law which states: that for every action there is an equal and opposite reaction |
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| this type of force results when two or more forces are acting along the same line |
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| this type of force occurs in the same plane and in the same or opposite directions |
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| this type of force results when two or more forces must act on a common point but must pull or push in different directions, such as two people pushing on a cabinet |
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| This force occurs as the overall effect of two forces acting on each other; occurs somewhere in between (occurs b/c of a concurrent force). |
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| this occurs when two or more forces act in different directions, resulting in a turning effect (rotation of the scapula) |
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| the amount of force needed by a muscle contraction to cause rotary joint motion |
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| TorF: Torque is greatest when the angle of pull is at 90 degrees, and it decreases as the angle of pull either decreases or increases from that perpendicular position? |
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| No torque is produced if the force is directed exactly through the axis of rotation. (i.e., if the biceps contracts when the elbow is nearly or completely extended, there is very little torque produced) |
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Definition
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| this type of force occurs when nearly all of the force generated by muscles is directed back into the joint (no torque is produced b/c the force is directed exactly through the axis of rotation) |
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Definition
| this type of force occurs when a muscle creates a large torque arm and line of pull (increased perpendicular distance), in that most of the force generated by the muscle is directed at rotating, not stabilizing, the joint |
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| this type of force occurs when the angular force goes beyond 90 degrees, causing the stabilizing force to become a ______ force, b/c the force is directed away from the joint |
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| TorF: a muscle is most efficient at moving, or rotating, a joint when the joint is at or near 90 degrees? |
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| GREATER moment arm= GREATER angular force. |
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Definition
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| GREATER stabilizing force = SMALLER moment arm |
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| If the joint angle is nearer 180 degrees, the moment arm is SMALL and the force is dislocating, pulling the two bones away from each other. |
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| Moment arm, size of the muscle, and contractile strength of the muscle all determine how effective a muscle is in causing joint motion. |
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| When an object is balanced, all torques acting on it are even and it is said to be in a State of ________. |
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| the mutual attraction b/t the earth and an object |
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| What is always directed vertically downward, and toward the center of the earth? |
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| the balance point of an object at which torque on all sides is equal |
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| in the midline at about the level of, though slightly anterior to, the second sacral vertebra of an adult |
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Definition
| Where is the COG located in the human body? |
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| TorF: the COG of a child is lower than that of an adult? |
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| The length of an adult's outstretched arms is equal to his or her height. |
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| the part of a body that is in contact w/ the supporting surface; if you outlined the surface of the body in contact w/ the ground you will have identified this term |
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| an imaginary vertical line passing through the COG toward the center of the earth |
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| This state of equilibrium occurs when an object is in a position where disturbing it would require its COG to be raised. |
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Definition
| This state of equilibrium occurs when only a slight force is needed to disturb an object. |
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Definition
| This state of equilibrium exists when an object's COG is neither raised nor lowered when it is disturbed. (i.e., a ball-as a ball rolls across the floor, its COG remains the same) |
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| The lower the COG, the more stable the object. |
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Definition
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| The COG and LOG must remain w/in the BOS for an object to remain stable. |
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| Stability increases as the BOS is widened in the direction of the force. |
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| The greater the mass of an object, the greater its stability. |
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| The greater the friction b/t the supporting surface and the BOS, the more stable the body will be. |
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| People have better balance while moving if they focus on a stationary object rather than on a moving object. |
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Definition
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Term
1)Lever
2)Pulley
3)Wheel and Axle
4)Inclined Plane |
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| Name the four simple machines used to change the magnitude or direction of a force. |
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| The basic rule of all simple machines is that the advantage gained in power is lost in distance. |
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| What is the basic rule for machines? |
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| this is rigid and can rotate around a fixed point when a force is applied (i.g., a bone, scissors, crowbars, manual can openers, wheelbarrows) |
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| axis (A), sometimes referred to as the fulcrum |
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Definition
| the fixed point around which the lever rotates (i.e., a joint in the body) |
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| force (F), sometimes called the effort |
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Definition
| What causes a lever to move? |
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| resistance (R), sometimes called the load |
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Definition
| this must be overcome for motion to occur and can include the weight of the part being moved (arm, leg, etc.), the pull of gravity on the part, or an external weight being moved by the body part |
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| When determining a muscle's role (force or resistance), it is important to use the point of attachment to the bone, not the muscle belly, as the point of reference. When determining the resistance of the part, use its COG. |
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Definition
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| the distance b/t the force and the axis |
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| the distance b/t the resistance and the axis |
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Definition
| this lever occurs when the axis is located b/t the force and the resistance |
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| TorF: In a first-class lever, if the axis is close to the resistance, the RA will be shorter and the FA will be longer; therefore, it will be easy to move the resistance. |
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| 1)it is easy to move the resistance 2)the resistance is moved only a short distance 3)the force to be applied through a long distance |
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Definition
| Fun Fact: first-class lever with a longer FA and shorter RA |
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| 1)is is harder to move the resistance 2)the resistance moves a longer distance 3)the force is applied through a short distance |
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Definition
| Fun Fact: first-class lever with a short FA and longer RA |
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| With a longer FA, the resistance will be easier to move, but the FA will have to move a greater distance. |
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Definition
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| The longer the RA, the harder it is to move the part. With the longer RA, the part won't have to move as far, but it will be harder to move. |
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| Fun Fact: RA (resistance arm) |
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| This lever occurs when the resistance is in the middle, w/ the axis at one end and the force at the other end (i.e., wheelbarrow). |
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| this lever occurs when the force is in the middle, w/ the resistance and the axis at the opposite ends (i.e., a person moving one end of a boat either toward or away from a dock) |
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| What is the most common lever in the human body? |
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| TorF: third-class levers favor distance and second-class levers favor force? |
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| Probably b/c the advantage gained from increased speed and distance is more imp than the advantage gained from increased power. |
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| Why are there so many third-class levers and so few second-class levers in the body? |
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Definition
| What consists of a grooved wheel that turns on an axle with a rope or cable riding in the groove? |
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| this type of pulley is a simple pulley attached to a beam, which allows it to act as a first-class lever |
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Definition
| this type of pulley has one end of the rope attached to a beam; the rope runs through the pulley to the other end where the force is applied |
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| What is the purpose of a fixed pulley? |
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| to increase the mechanical advantage of force |
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Definition
| What is the purpose of a movable pulley? |
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Definition
| _____ ______ is the number of times a machine multiplies the force. |
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| this type of simple machine is a large wheel connected to a smaller wheel and typically is used to increase the force exerted |
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Definition
| TorF: Turning around a larger wheel or handle requires less force, whereas turning around a smaller axle requires a greater force |
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Definition
| What type of simple machine is a flat surface that slants? |
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| An inclined plane is used for wheelchair accessibility and it exchanges increased distance for less effort. |
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Definition
| What is the purpose of an inclined plane? |
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| The advantage gained in force (decreased effort needed) is lost in distance (longer ramp needed). |
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Definition
| What is the basic rule of simple machines? |
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