Linear motion Flashcards
scalar quantity
when measurements are described in terms of their size and magnitude
speed + distance
vector quantity
when measurements are described in terms of magnitude (size) and direction
weight
acceleration
displacement
velocity
momentum
mass
the quantity of matter the body possesses
mass x gravity=weight
distance
length of a path a body follows when moving from one position to another
distance=speedXtime
displacement
measured in metres and is the shortest route in a straight line between the starting and finishing position
speed
the rate of change of position
speed =distance/time
velocity
measured in meters/ second and is the rate of change of displacement
displacement/ time taken
distance time graph
shows distance travelled over a period of time
the gradient of a graph
changes in y axis/ changes in X axis
velocity time graphs and speed time graphs
indicate velocity or speed of performer or object per unit of time
gradient will help decide wether the performer is travelling at a constant velocity, accelerating or decelerating
acceleration
rate of change of velocity
measured in m/s2
when velocity increases, so does acceleration
change in velocity/time
momentum
mass x velocity
force
changes a body’s state of motion
external force
comes from outside the body
friction, air resistance, weight, gravity
internal force
applied when our skeletal muscles contract
e.g. quadriceps contract concentrically to extend the knee in a jump
Vertical forces:
weight
the gravitational force exerted on an object
weight= mass x acceleration
vertical forces:
reaction force
occurs when two bodies are in contacts with one another
newtons 3rd law: for every action, there is an equal and opposite reaction
friction
occurs when two or more bodies are in contact with one another
horizontal forces:
frictional force
static friction force:
the force exerted on one surface by another when there is no motion between the two surfaces
occurs before an object begins to slide (move)
sliding frictional force:
two bodies in contact with one another that may have a tendency to slide over each other.
factors affecting friction
surface characteristics of the two bodies in contact
e.g. sprinter wearing spikes increases friction
temperature of surfaces
e.g. sweeping action in curling increases temp and reduces friction
mass of objects
a larger mass has greater fricton
horizontal forces:
air resistance
a force that acts in the opposite direction to the motion of a body travelling through the air
air resistance depends on
the velocity of the moving body
the faster the movement, the greater the resistance
the cross sectional area of the moving body
the larger, the greater
e.g. cyclists crouch low to reduce air resistance
the shape and surface of a moving body
a streamlined shape has less resistance. so does a smooth surface
e.g. swimmers shave their body (reduce ‘drag’)
net force
resultant force acting on a body when all other forces have been considered
a balanced force:
when two or more forces acting on a body are equal in size but opposite in direction
e.g. when standing, weight force and reaction force are equal but in opposite directions so there is zero net force and no change in the state of motion
