Biomechanics Flashcards
what are forces
forces are pushes or pulls which enable us to start or stop moving, change direction or maintain balance
what are the characteristics of forces
- vector (magnitude and direction)
- point of application
- line of application
what is the force equation
force = mass x acceleration
what is a tensile force
pulling forces acting on the ends of an internal structure (muscles onto tendons onto bones)
what is a compressive force
pushing force acting on the ends of an internal structure (bones onto cartilage onto bones)
what is a free body diagram
all the external forces acting on an object represented on a diagram
what are colinear forces
same line of action; same or opposite direction
what are resultant forces
vector addition of two or more forces
what is the net force?
vector addition of all the external forces acting on an object
what are concurrent forces
- act through the same point of application but not on the same line
- resultant of two or more concurrent forces depends on both magnitude of each force and angle of application
what is newtons first law of motion
- inertia
- every body is either in a state of rest or in continued motion until external forces are applied to it
- inertia is the resistance of a body to a change in its motion
what is linear momentum
- objects mass multiplied by its linear velocity
- momentum = mass x velocity
- kg.m/s
what are unbalanced forces
the object will accelerate in the direction of the net force
what is newtons second law of motion
- external forces cause acceleration
- force = mass x acceleration
- if an object accelerates then a net external force must be acting on the object
- insertion
- muscle attachement that moves most (smaller mass), generally more distal
- origin
- muscle attachment that moves least (greater mass), generally more proximal
what is newtons third law of motion
to every action there is an equal yet opposite reaction
what is newtons law of gravity
- the force of gravity acting on an object is termed its ‘weight’
- all objects attract each other with a gravitational force
- w=mg (weight = mass x gravity)
what is the centre of gravity
the point through which the resultant force of gravity acts on a body and entire weight of body is balance
what is linear motion
in a straight line
what is rectilinear motion
all points move same distance by same degree
what is curvilinear motion
all points move same distance but different angle
what is angular motion
- things rotating around an axis
- e.g. cyclists legs
what are the ways to collect kinematic data
- inertial system
- most common
- attach to body kit
- electromagnetic system
- optical system
- balls attached to body and high speed cameras to monitor movement
what is a spatial reference system
catches and measures the location of a body in space at some instant in time
- most labs use cartesian coordinate system
what are the different 3D coordinates?
+Y = up
-Y = down
+X = right
-X = left
+Z = forwards
-Z = backwards
what is a scalar quantity
can be described by magnitude
e.g. mass, distance, speed and volume
what is a vector quantity
have both magnitude and a direction
e.g. velocity, force and acceleration
what is distance
- scalar quantity
- length of the path followed by an object in motion - direction of motion not considered
what is displacement
- vector quantity
- the straight line distance in a specific direction from initial position to the final position
what is speed
- measures the rate of motion
- scalar quantity
- speed = distance / time
what is velocity
- measures the rate of motion but in a specific direction
- vector quantity
- velocity = displacement / time
what is acceleration
- an object is said to accelerate if there is any change in its velocity
- this includes when an object speeds up, slows down, starts, stops or changes direction
- acceleration = change in velocity / change in time
- m/s^2
- can be positive or negative (deceleration)
what is momentum
momentum = mass x velocity
momentum will stay constant unless an external force acts upon the object/person
what is impulse
- impulse = force x time
- impulse = impact x time
- it is the area under the curve
- represents a NET external force and therefore produces a change in momentum
what is centric force
external force directed through an objects centre of gravity
what is eccentric force
an external force not directed through an objects centre of gravity
what is a force couple
forces that are equal in size but opposite in direction and do not act in the same line
what is a torque
the rotatory force when the line of action of a force does not pass through the axis of rotation
what is the moment arm
the perpendicular distance between the line of action of the force and a parallel line passing through the objects axis of rotation
what is the equation for torque
torque = force x moment arm
what is a human body lever
- a level consists of a rigid bar (bone) that rotates about a fulcrum (joint - axis of rotation)
- levers also involve ‘effort’ forces (muscles) that act to counteract ‘resistance’ force (weight/external pushes)
- lever systems are used to generate torques onto the joints and locate our limbs
what are the components of lever systems
- the lever arm (bones)
- the fulcrum or axis of rotation
- the force of the muscle
- the resistance of body weight
what is the equation for mechanical advantage
mechanical advantage = (length of force arm)/(length of resistance arm)
what is a first class lever
- axis of rotation is in the middle
- resistance and muscle force are applied on opposite sides
- mechanical advantage may be high (>1) or low (<1) depending on the length of the force arm in relation to the resistance arm
what is a second class lever
- when the resistance and muscle force are applied on the same side but the muscle force is further away
- always have a high mechanical advantage (>1) because the force arm is longer than the resistance arm
what is a third class lever
- resistance and muscle force are applied on the same side but the muscle force is closer
- always have a low mechanical advantage (<1) because the force arm is shorter than the resistance arm
- third class lever systems are designed for speed and range of movement
what is static equilibrium
both the external forces of an object and external torques, about an axis must sum to zero
