forces

Object Interaction

• Non-Contact Forces:

  • Gravitational: Attraction between masses.

  • Electrostatic: Force between charges (like-repel, opposite-attract).

  • Magnetic: Force from magnetic fields.

• Contact Forces:

  • Normal Contact Force: Acts perpendicular to the surface.

  • Friction: Acts between rough surfaces to oppose motion.

Vectors and Scalars

• Vectors: Have magnitude and direction (e.g., displacement, velocity, force, weight).

• Scalars: Have magnitude only (e.g., distance, speed, mass).

Force Diagrams

• Free Body Diagrams: Visualize force directions on an object.

• Scale Drawings: Arrow length represents force magnitude. If opposite forces are equal, the object is in equilibrium (constant velocity).

Dynamics and Terminal Velocity

• Skydiver/Vehicle: Initially, a driving force (weight or thrust) causes acceleration. As velocity increases, resistive forces (air resistance or drag) increase. Terminal velocity is reached when resistive forces balance the driving force, resulting in zero resultant force and constant speed ($F=ma$).

Rotation and Moments

• Moment: The turning effect of a force, calculated as:
  $\text{Moment} = Fd$
  Where $F$ is force and $d$ is the perpendicular distance from the pivot.

• Equilibrium: Occurs when the sum of clockwise moments equals the sum of anticlockwise moments.

Levers and Gears

• Gears: Transfer rotational motion. A larger secondary gear increases force but decreases speed; a smaller one increases speed but decreases force.

• Direction: The secondary gear always rotates in the opposite direction to the primary gear.

• Efficiency: Lubrication reduces friction and heat loss, increasing system efficiency.