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purplespottyfish
 3 years ago
three forces (and no others) act upon an object, which remains at rest. the forces are represented by the vectors P, Q and R where P=4i5j and Q=2i+9j. find the magnitude and direction of the vector
the answer options i got are magnitude 3.2 or magnitude 7.2 and the options i got for direction are 146.3 degrees. 56.3 degrees, 33.7 degrees, 33.7 degrees, 56.3 degrees or 146.3 degrees
purplespottyfish
 3 years ago
three forces (and no others) act upon an object, which remains at rest. the forces are represented by the vectors P, Q and R where P=4i5j and Q=2i+9j. find the magnitude and direction of the vector the answer options i got are magnitude 3.2 or magnitude 7.2 and the options i got for direction are 146.3 degrees. 56.3 degrees, 33.7 degrees, 33.7 degrees, 56.3 degrees or 146.3 degrees

This Question is Closed

brinethery
 3 years ago
Best ResponseYou've already chosen the best response.0"Remains at rest" always always always means: "Summation of the forces is going to amount to zero"

radar
 3 years ago
Best ResponseYou've already chosen the best response.0Sum P and Q. R will equal that sum times 1 As the total sum will be 0 a stated by brinethery.

purplespottyfish
 3 years ago
Best ResponseYou've already chosen the best response.0how do you tell the direction though

radar
 3 years ago
Best ResponseYou've already chosen the best response.0R will be 180 degrees from the sum of P and Q

purplespottyfish
 3 years ago
Best ResponseYou've already chosen the best response.0the answer options i got are magnitude 3.2 or magnitude 7.2 and the options i got for direction are 146.3 degrees. 56.3 degrees, 33.7 degrees, 33.7 degrees, 56.3 degrees or 146.3 degrees

m_charron2
 3 years ago
Best ResponseYou've already chosen the best response.1well, since P + Q will give you 6i + 4j, R will be 6i4j, so with this, you can calculate the magnitude with pythagoras, and the angle with tan(4/6)

purplespottyfish
 3 years ago
Best ResponseYou've already chosen the best response.0how would pythagoras work as you dont have the side, sorry but im totally lost here

m_charron2
 3 years ago
Best ResponseYou've already chosen the best response.1dw:1334598901478:dw Now, you know the components of the vector R, as radar stated, it's 180 opposite from P+Q. Since you already have the vector components, you can draw a right triangle and calculate everything with it. Do you see it?

m_charron2
 3 years ago
Best ResponseYou've already chosen the best response.1dw:1334599135199:dw

purplespottyfish
 3 years ago
Best ResponseYou've already chosen the best response.0i kinda see where you are coming from but i still cant see what i have got to put on each side cos i just got letters so how do i get a number degrees out of it or a magnitude

m_charron2
 3 years ago
Best ResponseYou've already chosen the best response.1i and j are unit vectors, which means that their length is 1. For the purpose of this, it's simply a triangle with sides 4 and 6. the angle can then easily be found, it's tan^1(4/6) and you adjust it, either adding a minus sign, or 180 degrees, depending on where it is. Since it's in the 4 quadrant, simply add a minus sign
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