Biomechanical Principles

Question 1

define force

Answer 1

a push or pull that alters or tends to alter the state of motion of a body

Question 2

what can a force cause a body that is at rest do?

Answer 2

cause it to move

Question 3

what can a force cause a moving body to do? (4)

Answer 3

• change direction
• accelerate
• decelerate
• change the object’s shape

Question 4

the equation for force:

Answer 4

force = mass x acceleration

Question 5

“internal forces are generally produced by _______________ muscle contraction”

Answer 5

concentric

Question 6

“external forces act on an object or structure from the ____________ ; they generally come from the _________________”

Answer 6

outside
environment

Question 7

list the five external forces

Answer 7

• gravity
• friction
• air resistance
• applied force
• reaction force

Question 8

what is gravity?

provide a sporting example wherein gravity is in significant effect

Answer 8

the force pulling objects towards the earth

example
a high jumper falling back to the ground

Question 9

what is friction?

provide a sporting example wherein friction is in significant effect

Answer 9

the force resisting motion between two surfaces

example
a sprinter pushing off the track

Question 10

what is air resistance?

provide a sporting example wherein air resistance is in significant effect

Answer 10

the force acting against motion through the air

example
a cyclist experiencing a drag

Question 11

what is applied force?

provide a sporting example wherein applied force is in significant effect

Answer 11

a force exerted by a person or object

example
a footballer kicking the ball

Question 12

what is reaction force?

provide a sporting example wherein reaction force is in significant effect

Answer 12

the force exerted by a surface supporting an object

example
the ground pushing back on a gymnast’s hands during a handstand

Question 13

define linear motion (2)

Answer 13

• refers to movement in a straight line, wherein an object moves along a path in one direction
• all parts of the object travel the same distance in the same amount of time

Question 14

define angular motion (2)

Answer 14

• movement around a fixed point or axis; i.e. rotational
• different parts of the body may travel different distances but all rotate around the same axis

Question 15

define general motion (2)

Answer 15

• a combination of linear and angular motion
• one part of the body may move linearly whilst other points rotate around an axis

Question 16

there are three laws of motion, according to isaac newton.

what are each of them known as?

Answer 16

newton’s 1st law
law of inertia

newton’s 2nd law
law of acceleration

newtons 3rd law
law of action and reaction

Question 17

define inertia

Answer 17

the reluctance of an object to change its state of motion

or

the tendency of an object to remain unchanged

Question 18

law of inertia explains that…

provide an example wherein the law of inertia is shown within sport

Answer 18

an object will remain at rest or moving at a constant velocity unless acted upon by an external force

in a penalty, the football will remain stationary unless an individual kicks it or the wind happens to act upon it

Question 19

law of acceleration explains that… (3)

Answer 19

the force acting on an object is equal to the mass of that object multiplied by its acceleration

• the greater the force, the more the object accelerates
• the larger the mass, the harder it is to accelerate

Question 20

law of action and reaction explains that… (2)

provide an example wherein the law of action and reaction is shown in sport

Answer 20

• for every action, there is an equal and opposite reaction
• when two objects interact, the force exerted on one another is of equal magnitude but different direction

a sprinter pushing against the blocks

Question 21

the equation for speed:

Answer 21

speed = distance ÷ time

Question 22

define momentum

Answer 22

the quantity of motion; this is a product of mass and velocity

allows us to understand how mass and velocity influence the movement of athletes and objects

Question 23

how can momentum be increased in sport, for example?

Answer 23

using a heavier mass
heavier bat in cricket
heavier club in golf

increased velocity
running faster in football

Question 24

the equation for momentum:

Answer 24

momentum = mass x velocity

Question 25

define **impulse**

Answer 25

**a change in momentum** how force and time can cause the athlete to start moving or change direction

Question 26

the equation for impulse:

Answer 26

impulse = force x time

Question 27

"impulse is represented by..."

Answer 27

the area under a force-time graph

Question 28

define **positive impulse** provide a sporting example

Answer 28

when force is applied in the same direction as the motion of an object, increasing its velocity **e.g** ------------ a sprinter pushing off the starting blocks; the force applied in the forward direction

Question 29

define **negative impulse** provide an example

Answer 29

when force is applied in the opposite direction as the motion of an object, decreasing its velocity **e.g** ------------ a long jumper landing in the sand experiences a braking force from the ground

Question 30

define **net impulse** how is it calculated?

Answer 30

the overall change in momentum of an object; it takes into account both positive and negative impulses subtracting the total negative impulse from the total positive impulse

Question 31

so how does impulse change momentum in sport? (2)

Answer 31

**increasing momentum** athletes aim to generate positive impulse to increase momentum **decreasing momentum** athletes also use negative impulse to decrease their momentum

Question 32

what are the three ways in which a performer can increase impulse? (3)

Answer 32

- increasing the force applied - increasing the time the force is applied for (by utilising a follow through) - applying a greater force for a longer time

Question 33

define **stability**

Answer 33

the ability of the body or an object to return to equilibrium after being displaced

Question 34

define the **centre of mass/gravity**

Answer 34

the point at which the body is balanced in all directions

Question 35

define the **line of gravity**

Answer 35

an imaginary line that passes vertically from the centre of mass/gravity to the ground below an object

Question 36

define **state of equilibrium**

Answer 36

where a system remains unchanged and can return to its original state after a disturbance

Question 37

what are the four factors that affect **stability**?

Answer 37

- the mass of an object - the size of the base of support - height of the centre of mass - points of contact

Question 38

how does **mass of the object** affect stability?

Answer 38

**the greater the mass of the object, the more stable it is** *THIS IS BECAUSE,* a larger mass generates a greater force acting downwards due to gravity; increases inertia

Question 39

how does the **size of the base of support** affect stability?

Answer 39

**a larger base of support increases stability** *THIS IS BECAUSE,* the wider the area for the centre of mass to remain within, the more reduced chance of toppling over

Question 40

how does the **height of the centre of mass** affect stability?

Answer 40

**a lower centre of mass increases stability** *THIS IS BECAUSE,* the body's weight is distributed closer to the base of support and so this makes it harder for external forces to tip the body over

Question 41

how do the **points of contact** affect stability? (2)

Answer 41

- **more points of contact with the ground increases stability** *THIS IS BECAUSE,* weight is distributed more efficiently - **the greater the size of the points of contact increases stability** *THIS IS BECAUSE,* there is a greater surface area in contact with the object and therefore greater friction keeping them in place