Mechanics and Forces

  • Force is the interaction between two bodies

  • it represents quanities responsible for an objects motion

  • Can be contact or non contact


Types of Forces:

  1. Normal Force

  • The force exerted by a surface ON an object

  • There is always a normal force as long as there is contact between the object and surface

  • Perpendicular to the surface


  1. Frictional Force

  • Similar to normal force it is force that is being exerted on the object by the surface

  • Its direction is always opposite from the direction it is moving


  1. Tensional Force

  • Force that is exerted by cables or wires (Things that stretch essentially)


Netforce is the total number of forces ( the vector sum) applied on an object

  • We get the sum per components x and y

  • This is what tells us about the motion: At sum = 0 it is at rest/equilibrium, while negative represents downward/reverse and positive represents upwards/forwards


Mass and weight difference:
Mass is directly connected to the type of object it is

Weight is the gravitational force on a body


Newtons first law: INERTIA

An object stays at rest or stays in motion (at a constant velocity) unless an external force changes the state of the net force

  • Bali when something is at rest or in motion its net force is at equilibrium and it changes when other external factors act on the thing


Intertial Frame of Reference

  • It shows who observes the motion as motion is relative and depends on who is observing the “system” stationary on the ground

  • Also it shows whats happening ex: A car is at rest and you place a ball on the table, since at equilibrium the ball stays still it remains still, but when it accelerates forward the ball rolls backward, its not until the car reaches a constant speed/equalizes does the balll stop moving

  • Practical ex: sa train when its stopped you stand but when it accelerates forward you get pushed back, its like that until the train like reaches “constant” speed then it’ll feel like youre at rest again (equilibrium)


Newtons second law: External forces

  • The acceleration of an object depends on two variables, the net force on the object and its mass F=ma

  • Only valid if the mass is constant