Vector sample problem -- Force components on a spring mechanism

[sHatDowN]

Homework Statement

Resolve to its component

Relevant Equations

vector addition

Determine the amount and type (tensile or compressive) of the spring force so that the resulting force is a vertical force. Also get the resultant force.

i find 60N (compressive)
and resultant forces is 10800
is that correct?

 

[haruspex]

Homework Statement:: Resolve to its component
Relevant Equations:: vector addition

Determine the amount and type (tensile or compressive) of the spring force so that the resulting force is a vertical force. Also get the resultant force.

View attachment 323126

i find 60N (compressive)
and resultant forces is 10800
is that correct?

The exerted force is given in lb, not N.
How did you determine the spring is compressed?
How did you calculate the resultant?

 

[sHatDowN]

How did you determine the spring is compressed?

First, i calculate F_x,Then we apply opposite force.

How did you calculate the resultant?

R=F²+F_x²-2(F)(F_x)cos120

 

[sHatDowN]

Actually,Its √10800
=103.92

 

[erobz]

Actually,Its √10800
=103.92

Your magnitude is ok. I would have just noted that for $R$ to be vertical the force applied by the spring is opposite the component of $F$ in the horizontal direction ${}^+ \leftarrow, {}^+ \downarrow$:

$$ F_s = - F \cos 60° = -60 ~[\rm{lbf}]$$

$$R = F \sin 60° = 60 \sqrt{3} ~ [\rm{lbf}]$$

Which is what you have.

However, is the spring in tension or compression when it is applying the force $F_s$?

 

[Lnewqban]

... Determine the amount and type (tensile or compressive) of the spring force so that the resulting force is a vertical force.

The represented guide for that wheel (pushing or pulling the spring) is limiting the direction in which the spring is receiving any force, which is horizontal, rather than vertical.

 

[sHatDowN]

The represented guide for that wheel (pushing or pulling the spring) is limiting the direction in which the spring is receiving any force, which is horizontal, rather than vertical.

Yes, you right thanks a lot

 

[erobz]

Did you change your mind about it being in compression?

 

[sHatDowN]

Yes, thanks a lot.

 

[haruspex]

The represented guide for that wheel (pushing or pulling the spring) is limiting the direction in which the spring is receiving any force, which is horizontal, rather than vertical.

You misunderstand the question. It is asking what horizontal force from the spring will produce a vertical force when combined with the applied force F (and whether the spring will be in tension or compression). Which is a complicated way of asking for the force on the spring in equilibrium.