WEEK 6 Flashcards
define a force and describe
def= anything that causes a change in an objects status of motion
- unless a force acts on an object it will stay as it is
- push or pull activity that can cause an object to start, stop, speed up, slow down or change direction.
- magnitude (newtons
- direction (vector)
define the newtons law of motion
the relationship between forces and movement
moving an object from rest indicates there is an acceleration
- speeding up or slowing down an already moving object also indicates acceleration
identify newtons first law and define it
- law of inertia
def= a body in motion will stay in motion and body at rest will stay at rest unless acted upon by a net external force.
identify newtons second law and describe it
- a force that accelerates an object
- this acceleration is proportional to the force and inversely proportional to the objects mass.
describe weight versus mass
- weight is the force of gravity acting upon an object
- object weight is the product of that object mass and the earths gravitational constant
define and describe newtons third law
def= law of action reaction- for every action, there is an equal and opposite reaction
1) the force on each body is the same size Burt in opposite directions
2) true even when the bodies are significantly different mass
what are the peak vertical ground reaction forces for walking, running , jumping and swimming
walking= 1.2 x body weight
running= 3-4 x body weight
jumping= 7-9 x body weight
gymnastics= < body weight
- the action force must be greater than the objects resistance for motion to occur
- or a change in motion (acceleration, deceleration, change in direction) of that object
define internal forces
act within the object or system whose motion is being investigated
define external force
act on an object as a result of its interaction with the environments surroundings
- external forces can be described as non contact or contact forces
- non contact= forces that occur even if the objects are not touching
describe contact forces
def= occur between objects in contact with each other
- The objects in contacts can either be a solid or fluid
- air resistance
a contact force contains 2 components:
1) the NORMAL contact force
2) this force is perpendicular to the surfaces in contact
define a friction contact force
this force is parallel to the surfaces in contact and opposes motion or sliding between the 2 surfaces
define concurrent forces
forces that do not act along the same line, but act through the same point
define colinear forces
forces that have the same line of action for example tug of war.
- can be in the same of different directions
identify the two types of friction
- static
- kinetic= sliding and rolling
define static friction
friction between the contracting surfaces of two stationary objects. friction provides the resistive stationary objects
define kinetic friction
friction between contacting surfaces of two objects ( one object must be moving)
- can be a stabiliser of the motion of an object
- can also often decrease stability
static versus kinetic friction
maximum static friction= force required to initiate motion
kinetic= force required to maintain motion
calculate friction force
the magnitude is proportional to the friction co efficient and the normal reaction force.
what are the two types of friction and define each
sliding friction= friction force created when two surfaces slide and rub against each other
rolling friction= friction when one surface rolls over a supporting contact surface
what is the role of friction in certain sports (athletic shoes, skis, racquet grip and talcum powder)
athlete shoes= materials used in the soles have a large co efficient of friction to increase frictional forces when used
skis= waxing the bottom of the skis decrease friction on the snow
racquet grip= large frictional force to help maintain the group
talcum powder= increase friction during weightlifting , gymnastics
define equilirbirum
the state in which the net force acting on a system is 0. hence it maintains a current status of motion.
define static equilibrium
the object remains still
define dynamic equilibrium
the object moves with a constant velocity
