How to work out whether the value on a distance/velocity/acceleration vs time graph is meant to be +vs or -ve?
If a graph has a positive slope, then the value on the graph below will be positive, and if the graph has a negative slope, then the value on the graph below will be negative.
Are the following vector or scalar: Position, distance, displacement, speed, velocity, change in motion (speeding up/slowing down), acceleration?
Scalar: position, distance, speed, change in motion (speeding up/slowing down).
Vector: displacement, velocity, acceleration.
What is kinematics?
How objects move/ the features or properties of an objects movement (e.g. velocity, position, acceleration).
What is kinetics?
Why objects move/what makes objects move (e.g. forces and torques).
What is Newtons first law?
Law of inertia - An object in motion stays in motion unless acted upon by an external force.
What is Newton’s 2nd law?
Law of Acceleration (F=ma) - An objects acceleration is proportional to the force put in and acts in the same direction as the force. And with a given force, mass and acceleration are inversely related.
What is newtons 3rd law?
Law of Action/Reaction - For every action force exerted on an object by a second object, there will be an equal and opposite reaction force exerted on the 1st object.
1N will _ a _kg objects _ by _ every second.
1N will increase a 1kg object’s velocity by 1m/s every second.
What is gravitational force?
The attraction between 2 objects, determined by their masses (proportional) and the distance between them (Inversely proportional).
Gravitational constant = _
6.7x10-11 m3/kg/s^2
Equation for calculating gravitational force:
F = G ((m1* m2)/r^2)
What orientation to the ground does Normal/GRF act?
Perpendicular to the ground.
What orientation to the ground does friction force act?
Parallel, points opposite direction object is moving.
What % of the gait cycle is the swing phase?
40%
What % of the gait cycle is the stance phase?
60% (This includes the double stance phase which is 10%)
Describe how vertical GRF changes over the stance phase:
2 peaks: 1) Loading bodyweight onto stance limb to decelerate COM (which was moving downwards) causes an opposing large upward reaction force. 2) Propulsive impulse generated during toe-off.
1 trough: When COM is directly over the COP and vertical acceleration is momentarily 0.
Describe how horizontal GRF changes over the stance phase:
Initial positive (anterior) claw back to help us grab onto the ground with our heel -> Heel-strike acts as a braking impulse (negative, posterior) -> Toe-off acts as a propulsive impulse (positive, anterior).
Describe how mediolateral GRF changes over the stance phase:
Initial small lateral peak during early stance (a part of loading) -> Bigger medial peak during mid-stance (allowing COM to move over foot COP).
