3.2.2.3 Linear motion Flashcards
vector quantity
both magnitude and direction
e.g.s displacement, velocity, force, weight, momentum, angular displacement, angular velocity
scalar quantity
magnitude only
e.g.s distance, speed, mass, angular distance, angular speed, temperature
distance vs displacement
distance: length of path taken from 1 position to another (m)
displacement: shortest route in straight line route between 2 positions (m) (velocity x time)
speed vs velocity
speed: rate of change of body’s movement per unit of time (m/s) = distance divided by time
velocity: rate of change of displacement (m/s) = displacement divided by time
linear motion
motion in straight or curved line
parts moving same distance at same speed in same direction
centre of gravity along a straight/curved movements = in the same direction
vector diagrams
represent movement
- point of application
- line of application
- direction
length of arrow = magnitude
e.g. tennis ready position
no movement
weight force & ground reaction force
zero net force = state of inertia (N1)
GRF = W
vertical forces
- weight
2. reaction force (when 2 bodies in contact)
e.g jumping up
weight force and GRF direction of movement (DOM) upwards net force up, upwards acceleration GRF> W N2 more force = more acceleration F=ma (m - constant)
horizontal forces
- friction
2. air resistance
e.g. 200m sprinter
accelerating direction of movement to right
point of origin for air resistance is at COM
friction (anti slipping force)
F>AR
net forward force
acceleration
e.g. cycling
F=AR zero net force constant velocity (no vertical movement) GRF = W
e.g. runner
AR >F
net backwards force
deceleration
external force
comes from outside the body
e.g. friction, air resistance, weight, gravity
internal force
inside the human body e.g. contraction of muscles
generated by skeletal muscle
internal muscular force: from quadriceps as concentrically contract
frictional force
stops athlete slipping
e.g. sprint = max friction to stop slipping
static: no motion between surfaces
sliding: moving relative to one another
affected by:
- surface characteristics of 2 bodies in contact
- temperature of 2 surfaces
- mass of sliding objects
air resistance and what its affected by?
opposes motion through air
affected by:
- velocity of moving body
- cross sectional area of moving body
- shape/surface characteristics of moving object
impulse
time it takes a force to be applied to an object or body
relevant when 2 objects collide= impact
greater impulse = greater change in momentum
impulse is a product of
size of force acting
time the force is applied for
I = Ft
force time graph
impulse = area under force time graph
above the line = positive impulse
below the line = negative impulse
how does increasing impulses help?
momentum = velocity (outgoing) = acceleration
gradually decrease incoming momentum
e.g. cushioning a catch/crash matt
net impulse
combination of positive and negative impulses
mass vs weight
mass: quantity of matter the body possesses
weight: gravitational force exerted on an object
gravitational pull of athlete to the ground (increase mass = increase gravitational pull)
(mass x gravity = weight) (kg x 9.8 = N)
distance time graph
straight = stationary
increasing straight = constant speed
curved increase = accelerating
curved decrease = deceleration
velocity and speed time graphs
straight = constant velocity
curved increase = increase velocity or accelerating
curved decrease = decrease velocity or decelerating
above and below line = above increase is accelerating above decrease is decelerating below line = change of direction
deceleration/acceleration
+ve acceleration
-ve deceleration
rate of change of velocity (m/s squared)
change in velocity divided by time
change in velocity equation
final velocity - initial velocity divided by time
momentum (kg m/s)
amount of motion of an object resulting from mass and velocity
mass (kg) x velocity (m/s)
larger mass and if travel at same velocity = greater momentum
in order for linear motion to occur…
force applied directly through COM
occurs alongside angular motion
force
push or pull that acts on a body to cause a change in its state of motion (newtons)
effect of a force
- rest to move
- moving body = change direction accelerate, decelerate
- change shape of an object (e.g. dive)
vertical force vs horizontal force
horizontal > vertical = horizontal trajectory e.g. sprinter
vertical > horizontal = vertical trajectory e.g. high jump
free body diagrams/vector diagrams
forces applied to object (body) = arrows
arrow must start at point of application of force
direction of arrow = indicate direction force applied
length line = magnitude of force
