3- Biomechanics Flashcards
How topspin in tennis causes the flight path to deviate (use airflow)
- UPPER: airflow is in the opposite direction to the spin of the ball
- UPPER: low velocity, high pressure
- LOWER: airflow is in the same direction to the spin of the ball
- LOWER: high velocity, low pressure
- gradient going from high pressure to low pressure
- as a result Magnus force acting downwards
- Flight path shortens and dips (less time in the air)
One benefit of using topspin in tennis
- hit the ball harder and it will still land in the court
- can deceive opponents
How does the speed of release and height of release affect the horizontal distance travelled by a projectile
- faster the speed of release the further the projectile travels
- The higher the release compared to landing the further the projectile travels
two factors affecting the size of the moment of inertia of a rotating body
- mass of the body
- distribution of mass
using a practical example describe the relationship between moment of inertia and angular velocity
Inverse relationship
- Tucked position in gymnastics somersault : low moment of inertia and high angular velocity
- Straight position in gymnastic somersault: high moment of inertia and low angular velocity
Define Angular Momentum
quantity of angular motion possessed by a rotating body
Define moment of inertia and the measurement used
resistance of the body to change its angular motion (kgm^2)
Define Angular velocity
rate of change in angular displacement
Four types of force acting on a cyclist while they pedal forwards
- Weight (Down from COM)
- Reaction (up from both wheels)
- Air resistance (backwards from COM)
- Friction (forwards from ground on both wheels)
Use angular analogue of Newtons 1st law of motion to explain how the skater can increase rate of spin
- skater brings arms or legs in (closer to longitudinal axis)
- reducing moment of inertia
- increasing angular velocity
- principle of conservation of angular momentum
- AM= MI x AV
How a ski jumper can apply Bernoullis principle to maximise the distance travelled
- adopts an aerofoil shape
- create an angle of attack (17 degrees)
- UPPER: air travels further
- UPPER: higher velocity and lower pressure
- LOWER: lower velocity and a higher pressure
- air travels from high to low
- Lift force created
What is the equation and the units for angular velocity
angular displacement / time
rads -1
Explain how a golfer creates a hook shot and the effect on the flight path
- Eccentric force
- causes side spin
- LEFT SIDE: higher velocity and lower pressure
- RIGHT SIDE: lower velocity and higher pressure
- air travels from high to low pressure
- Magnus force
factors other than mass that impact on the air resistance of a ball in flight
- velocity
- shape (more aerodynamic)
- greater frontal cross sectional area
- the smoother the surface
- spin
metric units of measurement for displacement and acceleration
Displacement: metres
Acceleration: m/s squared
Describe linear motion and angular motion
- linear motion : movement of a body in a straight or curved line
- Angular motion : movement of a body in a circular path
factors that affect the size of moment of inertia of the trampolinist during a somersault
- mass
- Distance/distribution of mass
Three factors that affect the horizontal distance travelled by a shot in flight
- Speed of release: greater speed
- Angle of release: just under 45 degrees
- Height of release: greater the release height
Explain the shape of the flight path of the shot putt
- parabolic flightpath
- weight is the dominant force (mass is high)
- Air resistance will be low
identify vertical forces acting on the gymnast and explain their relationship during the handstand
- weight and reaction
- W=R
- Forces are equal and opposite (net force = 0)
Define angular motion and how it is generated to produce a somersault
- movement of a body about an axis of rotation
- Force applied outside the COM (eccentric force)
Use the angular analogue of newtons first law of motion to explain the concept of conservation of angular momentum
- body will continue to rotate about it’s axis of rotation with constant angular motion
- unless an eccentric force is applied
- Angular momentum= moment of inertia x AV
- once in flight any change to the moment of inertia will cause change in the AV in order to conserve angular momentum
- the performer can change the moment of inertia by manipulating body shape.
Identify two types of spin and the effect of each on a table tennis ball in flight
- Top spin (ball to dip, comes down more quickly)
- Back spin (longer flight path, travel further)
Identify ways that a swimmer can minimise drag
- reduce frontal cross-sectional area
- streamline
- reduce surface affects (smooth surface)
- reduce speed
State Bernoulli’s principle and apply it to an F1 racing car
The higher the velocity of air flow the lower the pressure, all gases move from an area of high to low pressure (down a pressure gradient)
- Spoiler is used
- angle of attack 17 degrees
- low pressure high velocity under spoiler
- high pressure low velocity above spoiler
- therefore pressure goes from high to low
- enabling the car to hold the road and go round bends at higher speeds
A 4 × 400 metre relay race takes place on a standard 400 metre track and the baton is correctly passed between the four runners.
Calculate the distance covered and displacement of the baton during the race.
Displacement = 0
Distance = 1600 metres
Describe a first class lever with a sporting example
- the neck when heading a football
- the fulcrum is located in between the effort and the load
- effort: Muscles at the back of the neck
- load: The head
- fulcrum: the neck
Describe a second class lever with a sporting example
- a calf raise
- load is located between the fulcrum and the effort
- Load: body weight
- Effort: calf muscles
- Fulcrum: balls of the foot
Describe a third class lever with a sporting example
- elbow during a bicep curl
- effort is located between the load and the fulcrum
- Fulcrum: elbow
- Effort: bicep brachii
- Load: dumbell in hand
What is mechanical advantage
- ratio of effort arm to the load arm defines the mechanical advantage
- less effort is needed to move the load
what two lever systems provide mechanical advantages and are used for strength related movements
- first class and second class movements
What lever system provides a mechanical disadvantage and is used for movements that require speed and range of motion
third class levers
Define Newtons first law
- law of inertia
- An object will stay in uniform motion or at rest until an external force is applied
Define Newtons second law
- law of acceleration
- Force = mass × acceleration (F=MA)
Define Newtons third law
- law of reaction
- for every action (force) there is an equal and opposite reaction
