Fundamentals of Biomechanics - Week 2 Flashcards
What are the two branches of biomechanics?
kinematics and kinetics
What is kinematics?
variables that describe movements (displacement, velocity, acceleration)
What are the two types of kinematics?
linear and angular
What is kinetics?
forces that cause movements
What are the two types of kinetics?
linear force and angular torque
What is the difference between a scalar and vector quantity?
Scalar = magnitude only, eg mass, distance, speed, time Vector = magnitude and direction, eg force, displacement, velocity, acceleration
What is a scalar? Give an example
mass, distance, speed, time
What is a vector? Give us an example
force, displacement, velocity, acceleration
What are the three types of motion?
linear, angular and general
What is linear motion? Give an example.
translatory motion
What is angular motion? Give an example
rotation around an axis
What is general motion? Give an example
combination of both linear and angular
What is linear displacement? What is it measured in?
change in location from initial to final position; must include direction and distance in metres
How is linear displacement different to distance?
distance is the route taken, whereas displacement is a straight line drawn from the initial to final points
What is linear velocity? What is the formula?
the rate of change in displacement
velocity (v) = change in displacement (s)/change in time (t)
What is the difference between speed and velocity?
speed is how fast a person or object is going, it is scalar (magnitude only)
velocity is speed in a given direction, it is a vector (magnitude and direction)
Can you have negative velocity?
yes, it means movement in the opposite direction
How is instantanous velocity different to under-estimate average velocity?
more accurate calculation, the smallest point of time is isolated to work out linear velocity.
What is the first central differenceformula?
velocity in an instant = (displacement at frame AFTER instant - displacement at frame BEFORE instant) / (time at frame AFTER instant - time at frame BEFORE instant)
What is linear acceleration?
the rate of change in velocity
What is the formula for linear acceleration?
acceleration (a) = change in velocity (v)/change in time (t)
When is acceleration 0?
- at max velocity
- at rest
- when velocity is contant
What is force?
- pushes and pulls
- all movement ceases and occurs due to the action of forces
- acceleration and change in direction of an object
- stabilises the body
- measured in Newtons (N)
- vector - has magnitude and direction
What are the properties of a force?
- magnitude (N) - amount of force exerted
- point of application - where force is applied
- direction (in degrees or rad)
- line of action - path of the force
What are Newtons three laws of motion?
1: law of inertia
2: law of acceleration
3: law of reaction
Explain Newton’s first law of motion?
a body will remain at rest or in constant motion unless acted upon by a net external force
eg man on motorcycle won’t stop flying through the air unless a force hits him (fence, gravity, wind)
What is Newton’s second law of motion?
the change in motion of an object is propertional to the force impressed; and is made in the direction of the straight line in which it is impressed
force = mass x acceleration
What is Newton’s third law of motion?
to every action there is an equal and opposite reaction
What are the forces acting on the body?
weight due to gravity, muscle, reaction forces (ground reaction forces, joint reaction forces), friction, spring force, bouyancy, air resistance
What is mass?
the amount of ‘matter’ an object has, constant regardless of where you are, scalar, measuresd in kg
What is weight?
the force experienced by an object due to gravity
weight = mass x acceleration due to gravity (9.81m2), measured in Newtons (N), vector (direction is always down)
What is the formula for weight?
weight = mass x 9.81
Where are muscle forces exerted?
muscle forces are exerted at the point of application (origin/insertion)
What is the ground reaction force?
action force = weight force
weight = mass x acceleration due to gravity
How is breaking force reduced?
foot should fall under the body or behind the body so that the person is propelled forward
What are types of mechanical loading in the body?
compression, tension, shear, torsion, bending
