common mistakes : mechanics Flashcards
why isnt “Ta” included in the equation for the total clockwise moment ? ( left hand side equation)
remember: moment = force times distance
the pivot here is “A” and the distance that the force/ tension “Ta” is from the pivot= ZERO
as a result moment= force * distance–> moment= Ta * ZERO
as a result the moment about where Ta acts on the pivot A is ZERO thus its not included in the equation for the clockwise moment
general steps for moments in equillibrium
- equate vertical components ( you can find tensions this way ! )
- solve other shit
what mistake did i make here when trying to equate the clockwise and anticlockwise moments when trying to calculate “x” ? (remember, the pivot is assumed to be “b “
i assumed that the force “60g” was clockwise but in reality it was actually anticlockwise
why did i do this silly mistake? i forgot that the pivot was B . instead, i assumed that it moved clockwise since i wrongly assumed that the weight was rotating around A instead
NOTE: ALWAYS ASSUME THAT FORCES MOVE ABOUT 1 PIVOT, NOT MULTIPLE .!!!!!!!!!!!!!
What would you always do first when calculating moments
state the pivot and use that pivot ALL THE WAY THROUGH !
HOW DO YOU FIND R IN MOMENTS IF THEY ARE EQUAL OR A FACTOR OF ONE AND OTHER ?
EQUATE THE GODDAMN VERTICAL COMPONENTS ( UP AND DOWN) AND FIGURE R OUT
forgetting to use the addition formula in venn diagrams
or to get X U Y or X n Y
instead of writing gravity as N
WRITE THEM OUT AS “g”
EG “1.5g”
common mistake in READING the question
not taking notice of the NAMES that they are talking aobut
if they give an angle in the form eg “tan(thetA)”
then KEEP it in that form when doing calculatuons so you can simplify them
IN STATIC PARTICLES (IMPORTANT)
AND IN KINETIC PARTICLES
F UR
(ALWAYS)
F= UR
