Biomechics - Principles Flashcards
What is Newton’s first law of inertia?
A body will remain in a state of rest of constant velocity unless added by an external force.
What is an example of Newton’s first law in terms of an object?
A football will remain at rest on the penalty spot until the force is applied from the players foot.
What is an example of newtons first law in terms of the athlete?
A runner will remain at constant velocity in the middle of a race unless an unbalanced force act upon them. Acceleration or air resistance for example.
What is Newton’s second law of acceleration?
The acceleration of a body is proportional to the size of the force applied and takes place in the direction in which the force acts. Force = acceleration x mass.
What is an example of Newton second law in terms of the object?
The acceleration of a netball during a pass is proportional to the force from the players hand and is in the same direction as the force.
What is an example of Newton the second law in terms of the athlete?
The acceleration of the runner during the sprint finish is proportional to the size of the friction force generated in the same direction as that force.
What is Newton’s third law?
For every action, there is an equal opposite reaction.
What is an example of newtons third law in terms of the athlete?
The runner pushes backwards on the track and the track pushes forward on the runner (ground reaction force).
What is an example of Newton’s third law in terms of an object?
When serving a tennis player, push it downwards on the ground and the ground pushes upwards on the ball.
What is the centre of mass?
A point at which mass is distributed evenly in all directions.
What are the three things involved with centre of mass?
Stability – a measure of how a body is moved from a position of equilibrium or balance.
Line of gravity – an imaginary line extending vertically downward to the ground from the centre of mass.
Base of support – the area enclosed by the points of contact with the ground.
What are the four factors affecting stability?
- Low centre of mass – the lower we are to the ground and the shorter the line of gravity the more stable we are.
- Large base of support and points of contact with the ground: the bigger the base of support the more stable we are.
- Large mass: the larger the mass the larger our stability.
- Line of gravity in the middle of base of support
What is a force?
A push or pull that alters the state of motion of a body. There can be multiple forces acting on a body and the result of these forces can be balanced or unbalanced.
What is a balanced force?
When two or more forces acting on a body are equal in size the opposite direction, all forces cancel out.
What is an unbalanced force?
When two or more forces acting on the body, do not cancel out. This means a net force acts.
What is a net force?
The overall force acting on a body when all forces are considered. Also known as the resultant force.
What are the two vertical external forces?
- Weight: acts down from the centre of mass.
- Reaction: acts upwards from the point of contact with the ground in the reaction to all downwards forces.
What are the two horizontal forces?
- Friction: opposes to the sliding motion of one surface across another.
- Air resistance: acts against the direction of motion opposing the movement of the body through the air.
What are factors affecting friction?
- Roughness of surface or soul of footwear.
- Weight increases the ground reaction force
- Temperature: heated tires increased friction between their blood and the track.
What factors affect air resistance?
- velocity
- Frontal cross-sectional area.
- Streamlining and shape.
- Surface characteristics.
- Mass.
Where in a free body diagram does weight originate from?
The centre of mass
Where in a free body diagram does ground reaction force originate from?
All points of contact with the ground.
Where in a free body diagram does air resistance originate from?
Centre of mass.
