Biomechanics

Question 1

define linear motion and give an example for the two types

Answer 1

Linear motion is when a body uniformly moves the same distance, direction during the same time. E.g. running (straight line motion) or swinging a golf club (curvilinear motion)

Question 2

define angular motion

Answer 2

Angular motion is when a body is in motion around an axis. Can be around a fixed point such as the hips during running or the centre of gravity such as the back spin of a basketball. It is different to linear motion as not all parts travel the same distance and direction within the same time frame

Question 3

define general motion and describe the general motion of a person riding a bike

Answer 3

General motion is the combination of angular motion of specific parts of the body such as hips or shoulders to cause the body to move linearly (same direction, distance and time).

The biker is using the angular motion of the hips and ankles as well as wheels and pedals of the bike to cause the bike and human body to move linearly. The combination of these two motions causes general motion.

Question 4

name 3 uses of biomechanics

Answer 4

video analysis
computer analysis
force platforms
streamlining body position
refining swimming technique
measure muscle force

Question 5

what is the difference between speed and velocity

Answer 5

speed is the rate that an object moves from one point to another (distance/time)

velocity is the displacement/time and has a direction while speed doesn’t

Question 6

define acceleration

Answer 6

rate of change of velocity

Question 7

define mass

Answer 7

the amount of matter that makes up a body

Question 8

define inertia

Answer 8

a body’s resistance to change of motion

Question 9

define force

Answer 9

the pushing and pulling action that changes a body’s motion

Question 10

what is the difference between distance and displacement

Answer 10

distance is the path an object takes from point a - b and displacement is the the distance in a straight line from point a - b

Question 11

define angular motion and give an example

Answer 11

angular motion is when a body moves around an axis or centre of gravity. This means that different parts of the body will travel at different speeds and distances. The parts of the body furthest away from the axis will travel the furthest and fastest.

an example of this is the angular motion of the femur around the hip joint when running.

Question 12

explain the four characteristics of sequential motion + draw graph

Answer 12

• use big muscle groups such as legs first
• accelerate each body part sequentially and fluidly to minimise energy “leaking” and optimise momentum transfer
• each body part is stable so that body parts accelerate over a stable base, further minimising energy leakage
• follow through so that the release is at maximum velocity and then decelerate after.
  graph:
• four crescents
• half way between
• legs + ankles -> hips -> shoulders + trunk -> wrist +arms
• x axis: timing and order
• y axis: level of performance
• title: ideal force + timing summation

Question 13

what is simultaneous movement

Answer 13

all body parts move simultaneously to maximise explosivity

Question 14

when would you use sequential motion and simultaneous motion

Answer 14

simultaneous: explosive movements e.g long jump
sequential: used in movements that require power and accuracy e.g three point shot in basketball.

Question 15

define force and give an example of a contact, non contact, internal and external force

Answer 15

a force is the pushing or pulling force on a body that can change its motion

contact: a player tackling another

non contact: gravity

internal: femur pressing down and tibia pressing up when landing from a jump (joint reaction force)
external: friction

Question 16

what forces affect a projectile

Answer 16

gravity

air resistance

air pressure

Question 17

what affect will changing the height, velocity and angle of release on a projectile’s trajectory

Answer 17

height of release: the projectile will have a higher max height and be in the air for longer which allows the horizontal motion more time to travel further

velocity of release: changing the velocity will have the most effect on horizontal displacement. Due to the projectile having a greater velocity gravity will have to overcome more force to push it down therefore the projectile will travel higher

angle of release: the optimum angle of release for horizontal displacement is approximately 45degrees but will have to be adjusted depending on external factors such as wind. the higher the angle of release the higher the max height will be.

Question 18

explain newtons first law.

Answer 18

law of inertia

a body’s will continue in a state of rest or motion unless acted upon by an external force.

an example of this is a golf ball on a tee. It will stay there forever unless acted upon by an external force such as wind or a club.

Question 19

explain newtons second law

Answer 19

law of acceleration

when an object is acted upon by a constant force the objects acceleration is proportional to its force and inversely proportional to it’s mass.

when a runner wants to maximise their acceleration they need to have big muscles to increase force production but also be lean because acceleration is inversely proportional to mass.

Question 20

explain newtons 3rd law

Answer 20

law of action and reaction

every force will have a force with equal magnitude and opposite direction

when running you will push down into the ground and the ground will push back with equal strength but opposite direction which will push you forward.

Question 21

what is balance and how can you maximise it

Answer 21

a body’s ability to maintain stability

the greater the mass the greater the stability

the greater area the object has with the ground, the greater the stability

keep the centre of gravity over base of support

keep centre of gravity low to the ground