Flashcards in Class test 2 revision Deck (26):
Newtons first law
A body continues in a state of rest or constant velocity unless acted upon by an external force
Newtons second law
Law of acceleration- the rate of change of motion (acceleration) of a body is proportional to the force acting on it and is in the direction that the force acts
Newtons third law
Law of action- reaction
For every action, there is an equal and opposite reaction
What is mass?
Quantity of matter a body possesses
What is force?
Mass x acceleration
What is the amount f force necessary to accelerate a mass of 1kg at 1m/sec
What is kinematics ?
Describes motion in terms of time and space
What is kinetics ?
Examines the forces
What is Newton's law of gravitation?
Every particle in the universe attracts every other particle with an attractive force
A body behaves as though all of its mass was concentrated at the centre of gravity. True or false
What do free body diagrams show?
Show all external forces
Forces drawn as vectors (direction and size)
What is equilibrium?
Describes the state of a system that is not changing its speed or direction
What is static equilibrium?
A body at rest
What is dynamic equilibrium?
A body that has unchanging speed or direction
What is stability?
Refers to the state of equilibrium
The ability of a body to maintain its beginning static equilibrium posture
What is the base of support?
The area made with the part of the body touching supporting surface
What is stable equilibrium?
Small perturbation applied- tends to return to its original position
What is unstable equilibrium?
Small perturbation applied- tends to accelerate away
What is neutral equilibrium?
Neither returns or accelerates
What happens to the centre of mass in a human body as a projector?
The centre of mass will follow path regardless of changes of body configuration
If an athlete wants to change direction quickly, should they have a small or large base of support?
When is an athlete most stable?
Low centre of mass
middle of base of support
Describe external forces
Act on objects as a result of interaction with surrounding environment
Contact/surface forces- occur between objects in contact
Non contact forces e.g. gravity
Describe internal forces
Act within the object
Do not accelerate the body
What is an eccentric force?
A force whose line of acion doesn't pass through the centre of gravity
Changes both angular and linear motion