Biomechanics - Subject Specific Vocabulary

Question 2

Define centre of mass

Answer 2

The point of balance of body or the point of concentration of mass.

Question 3

Define height of centre of mass

Answer 3

• Height of centre of mass: The lower an object’s centre of mass the more stable it is.

Question 4

Define area of base of support

Answer 4

• Area of base of support: The larger an object’s base of support the more stable it is.

Question 5

Define position of line of gravity

Answer 5

Position of line of gravity: The closer to the centre of the base of support an objects line
of gravity is the more stable it is.

Question 6

Define Newton’s 1st law of motion

Answer 6

A body will remain in a state of rest
or uniform motion until a force acts upon it.

Question 7

Define Newton’s 2nd law of motion

Answer 7

Acceleration is directly
proportionate to the magnitude of the force produced and is governed by the direction the
force is applied/ Force = mass x acceleration.

Question 8

Define Newton’s 3rd law of motion

Answer 8

For every action there is
an equal and opposite reaction.

Question 9

Define speed

Answer 9

The distance covered by a moving object in unit time taken. Distance divided by time.
Measured in metres per second (m/s).

Question 10

Define distance

Answer 10

The length of the space between two points. Speed multiplied by time. Measured
in meters (m).

Question 11

Define mass

Answer 11

The quantity of matter a body possesses. Density multiplied by volume. Measure in
kilograms (kg).

Question 12

Define a 1st class lever

Answer 12

1st class lever system: The fulcrum is in the middle. Examples in the human body include
extension at the elbow.

Question 13

Define a 2nd class lever

Answer 13

2nd class lever system: The resistance is in the middle. Examples in the human body include
plantar flexion at the ankle

Question 14

Define a 3rd class lever

Answer 14

3rd class lever system: The effort is in the middle. The most common example in the human
body includes flexion at the elbow.

Question 15

Define gravity

Answer 15

Gravity/Weight: Weight is gravitational force that the Earth exerts on the body. It acts
downwards.

Question 16

Define frictional force

Answer 16

Frictional force: The force that resists motion when the surface of one object comes into
contact with the surface of another

Question 17

Define air resistance

Answer 17

• Air resistance: A force which opposes the motion of a body moving through the air.

Question 18

Define impulse

Answer 18

The effect of a force acting over a period of time. Force multiplied by time. It is also a change in
momentum. Impulse is measured in newtons per second (Ns) reduced to kg/s.

Question 19

Define a vector

Answer 19

Quantities have both magnitude (size) and direction.

Question 20

Define weight

Answer 20

Weight: The gravitational force that the Earth exerts on the body. Mass x acceleration due
to gravity. It is measured in newtons (N).

Question 21

Define velocity

Answer 21

Velocity: The rate of change of displacement. Displacement divided by time. Measured in
metres per second (m/s).

Question 22

Define displacement

Answer 22

Displacement: The shortest route between the starting and finishing point. Calculated by
measuring a straight line between the two points. Measures in meters (m).

Question 23

Define acceleration

Answer 23

Acceleration: The rate of change of velocity or the difference between final and initial
velocities divided by the time taken. Measured in metres per second squared (m/s2).

Question 24

Define momentum

Answer 24

Momentum: The quantity of motion of a body. Mass multiplied by velocity. Measured in kg
m/s, or Ns.

Question 25

Define angular displacement

Answer 25

The smallest change in angle between the starting and finishing point of the rotation. Measured
in radians (rad). 1 radian = 57.3 degrees.

Question 26

Define angular momentum

Answer 26

The quantity of rotation a body possess. Moment of inertia multiplied by angular velocity.
Angular momentum is a constant.

Question 27

Define angular velocity

Answer 27

The rate of change of angular displacement. Angular displacement (rad) divided by time taken
(s). Measured in radians per second (rad/s)

Question 28

Define angular acceleration

Answer 28

The rate of change of angular velocity. Change in angular velocity (rad/s) divided by time taken
(s). Measured in radians per second squared (rad/s2
).

Question 29

Define moment of inertia

Answer 29

The resistance of a body to change its state of angular motion. Moment of inertia is a product
of an object’s mass and the distribution of this mass away from the axis of rotation. An object
with a greater mass or the same mass distributed further away from the axis of rotation will
have a higher moment of inertia

Question 30

Define horizontal displacement

Answer 30

The shortest distance from the point of release to the finishing point, in a straight line parallel
to the ground.

Question 31

Define parabolic flight

Answer 31

A symmetrical flight path eg a shot putt. A flight path which is not symmetrical, eg a badminton
shuttle, is known as non-parabolic flight.

Question 32

Define Bernoulli principle

Answer 32

Bernoulli’s principle describes the relationship between the speed and pressure of particles.
His principle states that an increase in the speed of particles occurs simultaneously with a
decrease in pressure.

Question 33

Define surface drag

Answer 33

Surface drag: Otherwise known as ‘skin drag’, this refers to the friction between the surface
of an object and the fluid environment.

Question 34

Define form drag

Answer 34

Form drag: Otherwise known as ‘shape drag’, this refers to the impact of the fluid
environment on the object. Forces acting on the leading edge of an object increase form
drag. Forces acting on the trailing edge reduce form drag.