Special type of vector diagram used to study the magnitude and direction of the forces acting on a body.
Newton Laws of motion
- Every body continue to be in rest or motion unless acted upon by external force
- F=ma
- For every force there is equal and opp force
What is weight?
- Weight is a force
- Mass x Gravity (Kg m/s2)= F (N)
- Means a person of 70kg will have a weight of 700N
- Should we care about these: NO
Levers
- Machine designed to move objects
- Bar
- Fulcrum
- 3 classes
Vectors
- Diagrammatic representation of force
- has magnitude and direction
Moments
- Force applied at distance from pivot will cause segment to rotate
- Distance is called moment arm
- Rotational effect is called turning moment
- Turning moment= F x moment arm
- also called torque
F x d=Moment
d
F
Assumptions
- 2d simplification of complex 3d structure
- we are using vectors and moments
- Body we draw is in equilibrium
- Bones are rigid rods
- Joints are frictionless hinges
- no antagonistic muse
- Force of muscle act through centre of muscle
- muscle act only in tendon
- JRF is compression only
- wt of body act through centre of mass