Dynamics Question

[kaanonball]

im not sure how to approach this problem, mainly because i am confused about the directions.

can someone show me how to solve part a) ?

[TrueTears]

I suggest make the 8N force the x axis, then just resolve normally along the x axis.

[You can make it the y axis if you wish, same principle.]

[zzdfa]

call the direction of 8N v
the 10N force does not contribute to the force in the v direction coz its perpendicular (if you resolve the 10N in direction of v you get 0.)

however the the 11N does contribute to the v direction; to find out exactly how much, you have to resolve the 11N vector in the direction of v. let the direction  of the 11N force be w. then the component of w in the direction of v is

(w dot v)/ abs(v)

now, we know that

(w dot v )/ abs(w)abs(v)   =  cos(angle between w and v)

abs(w) is 11and the angle between them is 115+90 = 205 degrees


so:

w dot v =11cos(205 degrees)

thats how much w contributes in the direction of v.

so the total is 8+88cos(205 degrees)

[kaanonball]

ahh thanks guys got it now =]

[kaanonball]

another question, im not sure how to draw the diagram can someone help?

[kamil9876]

Hint: represent the 10N force as 10i on a cartesian plane, while representing the others relative to that ie: the P N force could be -Pj (because 90degrees to 10i)

Using the info about the direction of resultant force, you should be able to see which components cancel out

[kaanonball]

Hint: represent the 10N force as 10i on a cartesian plane, while representing the others relative to that ie: the P N force could be -Pj (because 90degrees to 10i)

Using the info about the direction of resultant force, you should be able to see which components cancel out

thanks! i got it now =]

[kaanonball]

i can't get part b) of this question, can anyone show me how to do it using resolutions of forces

[kamil9876]

Use symmetry. The two forces can be represented as:

[kaanonball]

Use symmetry. The two forces can be represented as:

ahh thanks again kamil =]