4.3. Fundamentals of Biomechanics Flashcards
Define Speed
The rate at which an objects covers distance
Define Force
A force is a push or pull upon an object resulting from the object’s interaction with another object Mechanical interaction that goes on between two objects or bodies Forces change or tend to change the state of motion of an object
Define Velocity
“The rate at which an object changes its position” VELOCITY (m/s) (“v” if it is linear velocity) is a change in displacement divided by the time taken for the change to take place. It has size (how fast) and direction and so is also a vector quantity.
Define Acceleration
Acceleration is the rate at which an object changes its velocity. It is a change in speed, a change in direction or both. It is a change in velocity divided by the time taken for the change to take place. Vector quantity
Define Displacement
The difference between an object’s final position and starting position
Define Momentum
“The quantity of motion of a moving body, measured as a product of its mass and velocity” Momentum (kg.m/s) = Mass (kg) x Velocity (m/s)
Define Impulse
Impulse = Change in momentum Impulse = Force x Time F • t = m • ∆v
In a distance-time graph, the steeper the line…
…the greater the speed of the object
In a speed-time graph, the steeper the line…
… the greater the acceleration
Define Centre of mass
The point at which the mass and weight of an object are balanced in all directions Mathematical point around which the mass of a body or object is evenly distributed
Example of one activity where the centre of mass temporarily lies outside the body
Fosbury flop technique in high jump
Parts of a lever
Fulcrum (axis) Load (resistance) Effort
First class lever - definition and example
The fulcrum lies between the effort and the load Example: Head movement - neck (movement of the head about the atlas) The triceps - elbow joint (throwing)
Second class lever - definition and example
The load lies between the fulcrum and the point of effort Example: Ankle (plantar flexion - when walking or on tiptoes)
Third class lever - definition and example
The effort lies between the load and the fulcrum Example: Biceps curl
Newton’s first law of motion
The law of inertia Every body continues in a state of rest, or uniform motion in a straight line unless acted upon by an external or internal force to change that state. To achieve motion or bring about a change in motion, a force must be applied.
Newton’s second law of motion
The law of acceleration F= ma The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object
Newton’s third law of motion
The law of action/reaction For every action, there is an equal and opposite reaction
Define inertia?
Inertia is the natural tendency of an object to resist changes in motion
State the relationship between angular momentum, moment of inertia and angular velocity
Angular momentum=moment of inertia x angular velocity (You need to be able to explain these concepts and talk about conservation of angular momentum and implications for sports - for figure skating, for example)
Define angular momentum
Amount of angular (rotational) movement
Define moment of inertia
Body’s tendency to resist angular acceleration
Angular velocity
Rate of change of angular position of a rotating body
What happens when a skater opens their arms?
They increase moment of inertia and therefore angular velocity decreases (because angular momentum remains constant). They decrease speed (rotational)
What happens when a skater brings their arms close to the body?
Moment of inertia decrease and therefore angular velocity increases. They increase speed (rotational)
Factors that affect projectile motion at take-off or release
Speed of release Height of release Angle of release (You need to be able to explain each of them)
Bernoulli’s principle
The relationship between airflow velocity and air pressure is an inverse one, and is expressed in Bernoulli’s principle (you need to know examples) Bernoulli’s Principle states that as fluid velocity increases, pressure decreases (the relationship between air flow velocity and air pressure is an inverse one)
Explain projectile motion for a golf ball with backspin
A golf ball with backspin will experience higher air pressure on the bottom of the ball and lower air pressure on the top of the ball, causing a lift force (from high air pressure to low air pressure) (Include Bernoulli’s principle in your explanation)
Explain projectile motion for a golf ball with topspin
A golf ball with topspin will experience lower air pressure on the bottom of the ball and higher air pressure on the top of the ball, causing the ball to dip (from high air pressure to low air pressure) (Include Bernoulli’s principle in your explanation)
Which direction is Magnus force pushing the ball in this example?
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