BIOMECHANICS Flashcards
Define Newtons 3 laws of motion.
“A body continues in a state of rest or uniform velocity unless acted upon by an external force.”
“When a force acts on an object, the rate of change of momentum experienced by the object is proportional to the size of the force and takes place in the direction in which the force acts.”
“For every action, there is an equal and opposite reaction.”
What is Newton’s 1st Law of motion
This is also known as the ‘law of inertia’ and means that something will either stay still or stay moving unless a force acts on it. For example, a golf ball will remain still unless a force, applied by the golf club, makes it move. Or that same golf ball will continue to move at a constant velocity unless a force acts on it to slow it down (e.g. wind resistance) or change its direction (e.g. gravity).
What is Newtons 2nd Law of motion?
Put more simply, this means that when the golf ball, from the example above, is struck by the golf club the rate of change of momentum (or velocity) of the ball is proportional to the size of the force acting on it by the club. A useful way of writing Newton’s second law of motion, particularly when doing calculations, is Force = mass x acceleration (or F=ma).
What is Newtons 3rd Law of motion?
Or to put it exactly how Newton put it – ‘For every force that is exerted by one body on another, there is an equal and opposite force exerted by the second body on the first.’ This is sometimes referred to as the law of reaction.
For example, when a Tennis player hits a ball the racket exerts a force on the ball and the ball exerts an equal and opposite force on the racket. The racket exerts what is known as the action force and the ball exerts the reaction force which is felt by the player in the increased resistance at the time the racket strikes the ball.
What is force?
Pushing or pulling on an object that alters it current state of motion.
What is the equation for force?
What is it measured in?
Force = Mass x Acceleration
F=MA
Measured in Newtons (N)
Forces that act upon a body include…
Air resistance
Friction
Water resistance
Weight (of objects or other people)
What are the 5 effects of force?
Create motion Accelerate a body Decelerate a body Change the direction of a body Change the shape of a body
What is NET force?
What does it determine?
Overall force exerted on an object.
The different forces acting on a body are added together. Resulting in net force.
This will determine if forces are balanced or unbalanced.
What is balanced force?
What does it result in?
A sporting example.
When the multiple opposing forces on an object are equal.
This results in a constant state motion of an object as the net force equals 0.
Seen in a rugby scrum that doesn’t move due to equal force from both teams.
What is an unbalanced force?
What does it result in?
A sporting example.
When the multiple opposing forces on an object are unequal.
The object will move in the direction od the larger force (Newtons 2nd law)
Seen in a rugby scrum when one team applies greater force and the scrum will move forward.
What is weight?
What is it measured in?
Effect of gravity on an object is referred to as weight.
(not the same as its mass)
This pulls an object towards the ground when in flight.
Measured in Newtons (N)
F=MA
What is the equation for weight?
Weight = Mass (kg) x acceleration (9.81m/s2)
What is reaction?
Sporting example.
For every action there is an equal and opposite reaction. (Newton’s 3rd law).
If force exerted is larger than reaction force this creates upward movement.
When performing handstands the forces are balanced.
When jumping the forces are unbalanced
What is friction?
What is it measured in?
Sporting example.
Occurs during the interaction of two surfaces and opposes movement.
When grip is desired greater friction is needed.
(football studs allow better grip and controlled movements).
Measured in Newtons (N)
Some sports desire reduced friction such as skiing in order to travel quicker
