Biomechanical Principles & Linear Motion Flashcards
What is linear motion?
Movement in a straight line
How do you calculate speed?
Distance divided by time
How do you calculate velocity?
Displacement divided by time
How do you work out acceleration?
Change in velocity divided by time
Vf-vi / t
What is acceleration measured in?
m/s/s
Name Newton’s 3 laws of motion
1st - Inertia
2nd - Acceleration
3rd - Reaction
Describe Newton’s 1st Law
Inertia
a body continues in a state of rest or constant motion unless acted upon by an external force
Describe Newton’s 2nd Law
Acceleration
the rate pf change of momentum of an object is proportional to the size of the force applied
Describe Newton’s 3rd Law
every force exerted by one body onto another has an equal and opposite reaction
What is acceleration?
the rate of change of velocity
How do you calculate acceleration
change in velocity divided by time
vf-vi / t
What is acceleration measure in?
m/s/s
How do you measure velocity?
displacement divided by time
How do you measure speed?
distance divided by time
What is distance?
the path taken from point 1 to point 2
What is displacement?
the shortest straight line route from a to b (as the crow flies)
What is velocity?
how quickly you can move in a certain direction
What is speed?
how quickly you move
what are speed and velocity measured in?
m/s
If a distance/time graph is a straight horizontal line what does this show?
stationary
If a distance/time graph shows a straight diagonal line what does this show?
constant velocity
If a distance/time graph curves upwards to the right what does this show?
acceleration
If a velocity/time graph shows a straight horizontal line, what does this show?
constant velocity
If a velocity/time graph curves upwards to the right what does this show?
acceleration
Define the term ‘force’
a push or pull that alters the state of motion of a body
What is net force?
the overall force acting on a body when all the individual forces have been considered
What is a balanced force?
when 2 or more forces acting on the body are equal in size but opposite in direction. The resultant net force is 0
What is the resultant net force of a balanced force?
0
What is an unbalanced force?
When force acting in one direction is greater in size than a force acting in the opposite direction.
The resultant force is either positive or negative
Name the 2 vertical forces
weight and reaction
Name the 2 horizontal forces
friction and air resistance
What is weight force?
the force exerted on a body by the Earth’s attraction
What is weight measured in?
Newtons
What is reaction force?
for every action there is an equal and opposite reaction.
Where does the arrow on a free body diagram go for weight?
from the centre of mass (usually around the belly button) down to the floor
Where does the arrow on a free body diagram go for reaction?
from the points in contact with the floor upwards.
The bigger the force, the bigger the arrows
What is friction?
the force that acts in opposition to the movement of one surface over another
What is air resistance?
the force acting in the opposite direction to the motion of a body travelling through air
Where does the arrow on a free body diagram go for friction?
from the points in contact with the ground, forwards
Where does the arrow go on a free body diagram for air resistance?
from the centre of mass backwards
What factors affect friction?
surface characteristics
temperature of the two surfaces
How do surface characteristics affect friction?
rough surface (e.g. spikes on an athletics track) increases friction smooth surface (e.g. ski's on ice) reduces friction
How does temperature of the two surfaces affect friction?
an increase in temperature will either increase or decrease friction depending on the surface characteristics skis on snow - an increased temperature reduces friction rubber surfaces (e.g. tyres on a car) - an increase in temperature increases friction
What is the net force if AR = F?
net force =0 (balanced)
What is the net force and direction of motion if AR>F
direction of motion = forwards
net force = negative (unbalanced)
this means you are decelerating
What is the net force if AR
direction of motion = forwards
net force = positive (unbalanced)
this means you are accelerating
What is the net force if W = R?
net force = 0 (balanced)
What is the net force and direction of motion if W > R?
Direction of motion = downwards
net force = negative (balanced)
e.g. you are pushing down into the floor before take off for a jump
What is the net force and direction of motion if W < R
Direction of motion = upwards
net force = positive (balanced)
e.g. you are taking off of the ground in a jump
What is Impulse?
Impulse = a product of force x the time it acts for (Ns)
What can impulse be increased by?
greater muscular force = greater impulse
greater time a force is applied for = greater impulse
What do force/time graphs show?
Impulse
What does a negative section on a force/time graph for a high jumper at take off show?
pushing downwards into the ground
If the positive section of a force/time graph is greater than the negative section for a sprinter what does this indicate?
that they are accelerating
If the negative section of a force/time graph is greater than the positive section for a sprinter what does this indicate?
that they are decelerating
If the positive and negative sections of a force time graph are of similar levels for a sprinter what does this show?
they’re at a constant / maximum speed
