how do I know a force has to be perpendicular for it to be a minimal force?

Question

irishboy123 · Answer

what do you mean?

abmon98 · Answer

attachment

abmon98 · Answer

Why for the force P to be minimum it must be perpendicular to the resultant.

irishboy123 · Answer

they mean what is P such that the horizontal [left-right] bits cancel out leaving only a force in the up-down direction

irishboy123 · Answer

so resolve your forces in the horizontal or left-right bit,...., using trigonometry :p

abmon98 · Answer

i understand that the resultant acts upwards and that the net forces horizontally is 0.  If i resolved forces left-right i would come up with 2 unknowns, the angle and the magnitude of the force P. But according to the resolving the magnitude of P * its direction should equal (368.0)

irishboy123 · Answer

it says vertical, not upwards but i think that is a flaw in a question

if you resolve in vertical and specify that the net must be upwards, you have an equality and also an inequality, and 2 unknowns; so you can have a go at solving

anonymous · Answer

To distribute the force, I believe.