1 PP 11 Newtons Laws Part 2

Newton's Laws of Motion: Common Forces

Overview of Common Forces in Physics

• The weight force, denoted as W or F_g , represents the force of gravity acting downwards towards the Earth's core.

• Tension is a force present in ropes or strings, always pulling away from the object along the rope's direction.

• The normal force acts perpendicular to surfaces, pushing away from them and creating a right angle with the surface.

• Frictional force arises from surface roughness, opposing an object's motion; it acts opposite to velocity (e.g., left if moving right).

• Drag, represented by D , is caused by fluids (air or water), slowing objects down similarly to friction but occurs in liquids or gases.

Applied Force and Summation of Forces

• The applied force is exerted when a person pushes an object (e.g., a block).

• The summation of forces is indicated by a specific symbol that denotes adding all forces acting on an object together.

Free Body Diagrams Explained

• A free body diagram illustrates forces acting on an object; for example, a slide pulled at 30 degrees requires drawing vectors for each force.

• Identify contact forces touching the object; include weight (gravity), normal force upwards, and tension along the rope's direction.

• In frictionless scenarios (like ice fields), only three forces are considered: normal force up, weight down, and tension along the rope.

Example Problem: Block Sliding Down an Incline

• When analyzing a block sliding down a rough incline, draw its representation and identify gravitational weight pointing downward.

• Contact forces must be accurately depicted; ensure that normal force is drawn perpendicular to the inclined surface for correctness.

• Recognize that friction acts opposite to motion when sliding down; thus it opposes gravity while maintaining perpendicularity with respect to the surface.