Objectives You will be able to Differentiate and

Objectives You will be able to … ® Differentiate and describe the various types of forces we will be using in class.

Examples of Forces Ü Contact Ü At Applied Force (Fa, F#) ð Tension (FT, T) ð Normal Force (FN, N) ð Friction Force (Ff, f) ð Air Resistance (Fair) ð Spring Force (Fsp) ð a Distance Gravitational Force (Fg) ð Electrical Force (FE) ð Magnetic Force (FM) ð Nuclear Forces ð

Applied force [f#, fa, fb, f? ? ] ® Just any generic force in a problem ® Usually named after the object FJeska applying it. ® FBob ® FJeska ® Fdog ® Fpole ® Fwall ® FA … FB … F 17

Tension force [t, ft] ® An applied force where the force is applied through a string, cable, rope, etc. ® Special in the fact that a tension force can only pull, it cannot push. ® We usually assume the tension in a cable is the same everywhere in the cable.

Normal force [f. N] ® Contact interaction force between surfaces. ® Always acts perpendicular to the surfaces and out of the surface. ® Comes from the microscopic deformation of molecules modeling a system of springs. FN

Friction force [ff] Ü Comes from interactions with a surface as an object moves (kinetic) or tries to move (static) relative to the surface. Ü Depends on the normal force and a surface interaction constant called the coefficient of friction [ ]. Ü Always acts opposite the direction of motion. Ff Ff Surface

Air resistance force [fair] Ü Force that acts in a direction opposite motion through a gas. Ü Comes from cumulative interaction with air molecules. Ü Increases as the velocity through the gas increases. Ü Increases as the area normal to the direction of motion increases.

Spring force [fsp] Ü Comes from displacement of molecules. Ü Spring Force is always opposite the displacement of the spring. Ü A Force from a Hookean Spring is proportional to the displacement of the spring [ x] ð to the spring constant [k] (stiffness) ð

Gravitational force [fg] Ü At a Distance Force of attraction between ALL massive objects. FG, blue FG, orang e Ü Local gravitational constants g. Earth: 10 N/kg. ð g. Moon: 1. 6 N/kg ð g. Jupiter: 26 N/kg ð gyou: ~0. 00005 N/kg ð FG, red FG, green