Biomechanics Flashcards
What is normal force (Fn)?
the support force exerted by a surface, acting perpendicular to it (eg. a kettlebell sitting on the floor)
What are the parts of a lever? describe the purpose of each.
effort/force - the force applied to MOVE the load. can by applied by muscles, hands, or external forces
fulcrum - the fixed point around which the lever rotates (“hinge”)
load/resistance - the object or weight that needs to be moved; resists movement & influenced by gravity
What is inertia
the tendency of an object to resist changes in motion
** the more mass an object has, the more inertia it has (harder to stop or start its motion)
ex. a soccer ball won’t move until it’s kicked or a hockey puck keeps sliding on ice until friction or a stick stops it
What is buoyant force (FB)?
an upward force exerted by a fluid (liquid or gas) on an object placed in it (eg. a canoe floating on water)
Whats a class 2 lever? give an example
load is located between the effort and fulcrum or axis of rotation
ex. a wheel barrow
What is the second law of motion; the law of acceleration? How does it work in terms of force and mass?
the law that states a force applied to an object causes an acceleration of that object in the SAME direction of the applied force
~ acceleration is proportional to the magnitude of the force, but inversely proportional to the object’s mass
↑ force = ↑ acceleration (if you push harder, the object will accelerate more)
↑ mass = ↓ acceleration (heavier objects are harder to move; they accelerate less for the same amount of force)
What is lift force (FL)?
a force created by high and low pressure difference (eg. frisbee flying through the air)
Whats the first law of motion; The law of Inertia?
the law that states a body in motion tends to stay in motion and a body at rest tends to stay at rest unless acted upon by an unbalanced force
ex. a curling rock is released from the hand of the curler; if it were sliding on an frictionless surface, it would continue to move at the same speed indefinitely until an unbalance force acts on it
How is force a vector quantity?
force has a magnitude (measured by Newton’s (N)) and force also has direction
What are the three ways human physical activities involve rotational or angular motion?
- rotation of projectiles or other objects (ex. swinging a hockey stick)
- rotation of the entire human body about one of the three axis (ex. cartwheel)
- Rotation of individual body segments (ex. throwing motion of a baseball pitchers arm)
What is the third law of motion; the law of action-reaction?
the law that states that for every action, there is an equal and opposite reaction
~ whenever an object exerts a force on another object, the second object exerts an equal force in the opposite direction on the first object
~ forces come in pairs; if you push on something, it pushes back with the same force but in the opposite direction
What is the gravity force? (Fg)
the force of attraction between two objects due to their mass (eg. earths pulling balls downward)
Whats an external force?
forces originating outside of the object or body of what we are studying
~ we cannot always see these forces but we can feel them
~ ex. gravity, air/wind resistances, surface friction
What is a lever
a simple machine that consists of a rigid “bar” that pivots around a fixed point called a fulcrum
~ balance two or more forces
~ provide a force advantage, whereby less effort force is required to overcome a greater load/resistance force
~ provide an advantage in speed of movement, whereby the load to be moved moves farther and faster than the effort force
Whats a class 1 lever? give an example
a fulcrum is located between the load and effort
ex. a teeter totter
What is acceleration
the rate at which an object changes its speed/velocity
~ occurs when an object speeds up, slows down, or changes direction
What is angular motion (rotational)?
involves a rotation or a turning point around an axis
~ unlike linear motion, the force does not act through the centre of an object or body but rather is “off-centre”, and this results in rotation
ex. a basketball player pivoting around a planted foot OR a diver flipping
Whats an internal force?
arise within the system we are interested in studying (ex. human body)
~ muscle contractions generate force that results in movement (biceps brachii contracts creating a pulling force on the radius - elbow flexion)
What is centric force
force directly applied through the centre of an object and it will result in LINEAR motion (object will move in the direction the force was applied)
What are the complexities of linear motion
the linear motion of humans is often the result of the interaction of a combination of forces
What is linear motion (translational)?
when a body/object or the collective parts move the same distance, in the same direction, in the same amount of time
ex, the sprinter as a whole body moving down the lane towards the finish line
Whats a class 3 lever?
application of effort/force is BETWEEN the load and fulcrum
ex. lifting a shovel with a load of soil
What are the advantages of each class of lever?
class 1 - can multiply force or speed depending on placement of fulcrum
class 2 - always increases force (makes lifting easier)
class 3 - increases speed and range of motion (but requires more force - commonly found in human body)
What is tension force (Ft)?
a pulling force through a rope, cable or string (eg. pulling a slide with a rope)
