4.3. Fundamentals of Biomechanics

Question 1

Define Speed

Answer 1

The rate at which an objects covers distance

Question 2

Define Force

Answer 2

A force is a push or pull upon an object resulting from the object’s interaction with another object Mechanical interaction that goes on between two objects or bodies Forces change or tend to change the state of motion of an object

Question 3

Define Velocity

Answer 3

“The rate at which an object changes its position” VELOCITY (m/s) (“v” if it is linear velocity) is a change in displacement divided by the time taken for the change to take place. It has size (how fast) and direction and so is also a vector quantity.

Question 4

Define Acceleration

Answer 4

Acceleration is the rate at which an object changes its velocity. It is a change in speed, a change in direction or both. It is a change in velocity divided by the time taken for the change to take place. Vector quantity

Question 5

Define Displacement

Answer 5

The difference between an object’s final position and starting position

Question 6

Define Momentum

Answer 6

“The quantity of motion of a moving body, measured as a product of its mass and velocity” Momentum (kg.m/s) = Mass (kg) x Velocity (m/s)

Question 7

Define Impulse

Answer 7

Impulse = Change in momentum Impulse = Force x Time F • t = m • ∆v

Question 8

In a distance-time graph, the steeper the line…

Answer 8

…the greater the speed of the object

Question 9

In a speed-time graph, the steeper the line…

Answer 9

… the greater the acceleration

Question 10

Define Centre of mass

Answer 10

The point at which the mass and weight of an object are balanced in all directions Mathematical point around which the mass of a body or object is evenly distributed

Question 11

Example of one activity where the centre of mass temporarily lies outside the body

Answer 11

Fosbury flop technique in high jump

Question 12

Parts of a lever

Answer 12

Fulcrum (axis) Load (resistance) Effort

Question 13

First class lever - definition and example

Answer 13

The fulcrum lies between the effort and the load Example: Head movement - neck (movement of the head about the atlas) The triceps - elbow joint (throwing)

Question 14

Second class lever - definition and example

Answer 14

The load lies between the fulcrum and the point of effort Example: Ankle (plantar flexion - when walking or on tiptoes)

Question 15

Third class lever - definition and example

Answer 15

The effort lies between the load and the fulcrum Example: Biceps curl

Question 16

Newton’s first law of motion

Answer 16

The law of inertia Every body continues in a state of rest, or uniform motion in a straight line unless acted upon by an external or internal force to change that state. To achieve motion or bring about a change in motion, a force must be applied.

Question 17

Newton’s second law of motion

Answer 17

The law of acceleration F= ma The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object

Question 18

Newton’s third law of motion

Answer 18

The law of action/reaction For every action, there is an equal and opposite reaction

Question 19

Define inertia?

Answer 19

Inertia is the natural tendency of an object to resist changes in motion

Question 20

State the relationship between angular momentum, moment of inertia and angular velocity

Answer 20

Angular momentum=moment of inertia x angular velocity (You need to be able to explain these concepts and talk about conservation of angular momentum and implications for sports - for figure skating, for example)

Question 21

Define angular momentum

Answer 21

Amount of angular (rotational) movement

Question 22

Define moment of inertia

Answer 22

Body’s tendency to resist angular acceleration

Question 23

Angular velocity

Answer 23

Rate of change of angular position of a rotating body

Question 24

What happens when a skater opens their arms?

Answer 24

They increase moment of inertia and therefore angular velocity decreases (because angular momentum remains constant). They decrease speed (rotational)

Question 25

What happens when a skater brings their arms close to the body?

Answer 25

Moment of inertia decrease and therefore angular velocity increases. They increase speed (rotational)

Question 26

Factors that affect projectile motion at take-off or release

Answer 26

Speed of release Height of release Angle of release (You need to be able to explain each of them)

Question 27

Bernoulli’s principle

Answer 27

The relationship between airflow velocity and air pressure is an inverse one, and is expressed in Bernoulli’s principle (you need to know examples) Bernoulli’s Principle states that as fluid velocity increases, pressure decreases (the relationship between air flow velocity and air pressure is an inverse one)

Question 28

Explain projectile motion for a golf ball with backspin

Answer 28

A golf ball with backspin will experience higher air pressure on the bottom of the ball and lower air pressure on the top of the ball, causing a lift force (from high air pressure to low air pressure) (Include Bernoulli’s principle in your explanation)

Question 29

Explain projectile motion for a golf ball with topspin

Answer 29

A golf ball with topspin will experience lower air pressure on the bottom of the ball and higher air pressure on the top of the ball, causing the ball to dip (from high air pressure to low air pressure) (Include Bernoulli’s principle in your explanation)

Question 30

Which direction is Magnus force pushing the ball in this example?

Answer 30

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