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Forces and Free Body Diagrams (FBD). Forces. A force causes an object to change its velocity, by a change in speed OR direction Force is a vector quantity since direction is important
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Forces • A force causes an object to change its velocity, by a change in speed OR direction • Force is a vector quantity since direction is important • There are contact forces between objects that touch and there are field forces between objects that do not touch
Forces • SI Unit for Force is the Newton (N) • The formula for force is F = ma NOTE: the unit for mass is kg and the unit for acceleration is m/s2… so a kg•m/s2 is the same thing as a Newton!
Free Body Diagrams (FBD) FBDs are used to show relative magnitude and direction of all forces acting on an object in a given situation, therefore: 1. Draw the object as a box 2. The larger the force the longer the vector arrow should be 3. The direction of the arrow’s tip should show the direction that the force is acting 4. Always label your force vectors 5. With constant velocity vectors are equal and with acceleration/deceleration vectors are unequal
FBD Example A book on a table is being pushed to the right at a constant velocity
FBD Example A parachutist jumps out of an airplane; include air resistance
How would I draw the FBD? This is what the FBD should look like!