free body diagram

• this isolates the forces acting on an object for example an arrow upwards for up thrust and an arrow downwards for gravity
• 'normal' contact force means the force exerting on a right angle to the object (90 degrees)
• arrows are drawn to the same scale.... longer the arrow the larger the force
• object on inclined slope

  • forgetting friction
  • the only force acting on the object is its weight
  • this can be turned into 2 components parallel and perpendicular

  parallel - mgsin$\theta$

  perpendicular - mgcos$\theta$
• the components of w acting downwards is responsible for the objects acceleration down the slope.
• component of the weight = normal contact force, N

  N = mgcos$\theta$