Types of Forces, Hook's Law, Moment, COG, Centripetal Force

Types of forces

Contact e.g. normal force, non-contact e.g. gravitational force

Tip-to-tail

1. Keep Scale
2. Draw forces from tip to tail
3. Measure resultant force
4. Measure direction with protractor

Hook’s Law

Force (n) = k (spring constant, n/cm or n/m) * x (extension m or cm)

Another way to write force

m (kg) * g (10m/s)

Force formula

f (n) = m (mass kg) * a (acceleration m/s^2)

Acceleration (m/s^2)

v (final velocity m/s) - u (initial velocity) / t (time)

Vector addition

same direction add, different direction subtract

Moment

Moment (Nm) = Force (n) * Perpendicular Distance (m from pivot point)

Net moment

clockwise moment (f*d) - anticlockwise moment (f*d)

Principal of Moments

If an object is in equilibrium, sum of clockwise = sum of anti-clockwise

Example: Find distance to make equilibrium

CWM = ACWM
Moment = F*D

(140) (D) = (690) (0.3)
D = (690)(0.3)/(140)

COG

wider the base, more stable
Lower the cog, more stable

Centripetal force

If you increase r (radius), Fc (centripetal force) decreases

Increase v (velocity), Fc (centripetal force) increases

Increase m (mass), Fc (centripetal force) increases