Biomechanics - Motion

Question 1

What is linear motion?

Answer 1

The movement of a body in a straight line or curved line, where all parts move the same distance, in the same direction, over the same time. Created by a direct force that passes through the centre of mass of the body.

Question 2

What is the difference between distance and displacement?

Answer 2

Distance is the length of a path taken by a body moving from one position to another.
Displacement is the shortest straight line route between positions.

Question 3

What is speed?

Answer 3

The movement of a body per unit of time. Distance/time.

Question 4

What is velocity?

Answer 4

The rate of change of displacement in a given direction. Displacement/time.

Question 5

What is acceleration/deceleration?

Answer 5

The rate of change of velocity. Change in velocity/time.

Question 6

What are the 3 different graphs linear motion can be recorded by?

Answer 6

1. Distance/time
2. Speed/time
3. Velocity/time

Question 7

What is angular motion?

Answer 7

When a body moves in a circle or part of a circle about an axis of rotation.

Question 8

How is angular motion initiated?

Answer 8

Angular motion is created by an eccentric force which passes outside the centre of mass or axis.

Question 9

What is meant by moment of inertia?

Answer 9

The measure of an objects resistance to chances in its rotational motion around an axis.

Question 10

What is meant by angular velocity?

Answer 10

The rate at which an object rotates or spins around an axis, measured by how much the angle changes over time.

Question 11

What is meant by angular momentum?

Answer 11

The quantity of rotational motion an object has, depending on its mass, shape and how fast it’s spinning.

Question 12

How does mass affect moment of inertia?

Answer 12

• the larger the mass of the body the larger the moment of inertia.

Question 13

What is torque?

Answer 13

Measure of the turning force that causes an object to rotate around an axis.

Question 14

What is the effect of distribution of mass around an axis on moment of inertia?

Answer 14

The further the mass from the axis, the larger the moment of inertia.

Question 15

What is fluid mechanics?

Answer 15

The study of the factors that impact the magnitude of air resistance and drag. Air resistance and drag are both types of fluid friction and have a huge impact on the performance of all sports.

Question 16

What is air resistance?

Answer 16

The force acting to oppose the motion of a body through the air.

Question 17

What is drag?

Answer 17

The force acting to oppose the motion of body through a fluid.

Question 18

What are the effects of air resistance and drag?

Answer 18

• an athlete wants to put all of their energy into maximising performance and not waste it overcoming forces that hold them back.
• air resistance and drag act against the motion of a body and place and increased physiological a demand leading to early fatigue and poor performance.

Question 19

What are the 5 factors affecting magnitude of air resistance and drag?

Answer 19

Velocity
Front cross-sectional area
Mass
Streamlining and shape
Surface characteristics

Question 20

What is magnitude?

Answer 20

The size of a quantity.

Question 21

How does the magnitude of velocity affect drag and air resistance?

Answer 21

• the greater the velocity, the greater the air resistance or drag.
• high levels of velocity is beneficial to performance.

Question 22

How does the magnitude of mass affect drag and air resistance?

Answer 22

• the greater the mass, the less it’s motion is changed by these forces.
• bodies with small mass slow down quickly due to fluid friction.

Question 23

How does the magnitude of front cross-sectional area affect drag and air resistance?

Answer 23

• the smaller this area is the less fluid friction acts
• this is the areas of the part of the body that presents first to the fluid it is moving through.

Question 24

How does the magnitude of streamlining and shape affect drag and air resistance?

Answer 24

• optima; shapes and positions can make a body more streamlined and reduce air resistance and drag.
• this reduces turbulence and smooths the air or water flow around a body.

Question 25

How do surface characteristics affect drag and air resistance?

Answer 25

- smooth surfaces create less air resistance or drag than rough surfaces - this includes the human skin and hair

Question 26

How will a downhill skier minimise factors affecting drag and air resistance?

Answer 26

- minimise frontal cross-sectional area by adopting a low crouched position in the straights and jumps. - wear tear-drop shaped helmets and have fins on their gloves and around their boots to create a streamlined shape, easing the flow around their body. - they wear super silky lycra suits to create a smooth surface.

Question 27

How will a track cyclist minimise factors affecting drag and air resistance?

Answer 27

- light weight carbon fibre bike design with area dynamic features such as disc wheels and forks to reduce energy expenditure. - aerodynamic positioning with shoulders forward, high seat etc - aerodynamic helmets with a glossy surface and specialised shaped to streamline air flow -tight fitting lycra skin suits and smooth socks pulled over the shoes to seamlessly moult to the leg

Question 28

What is a projectile?

Answer 28

A projectile is a body that is moving within a fluid, not in contact with the ground. Fluids include air and water.

Question 29

What are the 3 factors affecting horizontal distance?

Answer 29

- height of release - speed of release - angle of release

Question 30

What are the two forces acting on a body during flight?

Answer 30

Weight and air resistance.

Question 31

What is a parabolic pattern of flight path?

Answer 31

A uniform curve that is symmetrical around its highest point.

Question 32

What is a non-parabolic flight path?

Answer 32

A curve that is not symmetrical about its highest point.

Question 33

What happens tot he resultant force during a parabolic flight path?

Answer 33

The resultant force changes very little during each phase of flight.

Question 34

What is an example of an object with a non-parabolic flight path?

Answer 34

Badminton shuttle cock.

Question 35

What happens to the resultant forces during a non-parabolic flight path?

Answer 35

The size and direction of the resultant force changes during flight.

Question 36

What causes something to move in a non-parabolic flight path?

Answer 36

Forces like air resistance and weight decreases the objects velocity, changing its flight path and making it asymmetrical.

Question 37

What is an aerofoil?

Answer 37

An object with a shaped designed to generate lift by creating a pressure difference as air flows over it, faster of the top (tends to be curved), and slower underneath

Question 38

What is Bernoulli’s principle?

Answer 38

Upwards lift force: - the upwards lift force reduces the impact of weight - the resultant force has a smaller downwards component - flight time is extended and therefore the horizontal distance travelled increases - the flight path is made non parabolic

Question 39

What is Magnus force?

Answer 39

The lift force created when a spinning sports object moves through the air. The spin changes air pressure around the object causing it to swerve or dip in the direction of spin.

Question 40

Explain Bernoulli’s principle in terms of a topspin in tennis

Answer 40

- at the top of the ball the airflow is in the opposite direction to spin, slowing the air particles causing high pressure - at the under side of the ball the airflow is in the same direction as the spin, speeding up air particles and causes low pressure - there is higher pressure above than below causing a downwards forces Magnus force, making the ball dip in flight.