Question

Find force!!

Answer 1

im not really sure do i have to find the answer exact or close to it? im getting 11.54N as my answer but the answer is supposed to be 10 N

Answer 2

@matt101 im so sorry it's like 3rd q and i have 4th coming up T_T

Answer 3

We are so sorry about calling you over and over again.

Answer 4

That's alright! Good timing I just came back on. I can tell you now the answer should actually be 20 N without doing any calculations. We're trying to find the value of F. F has horizontal and vertical components. The vertical component of F must be 10 N to balance the weight of the rod, and adding the horizontal force to that will produce a total force greater than 10 N. 20 N is the only option greater than 10, so that must be the answer.

But if you want to math it, use some basic trig:

\[10=F \sin 30\ \]\[F=\frac{ 10 }{ \sin 30 }\]\[F=20\]

Answer 5

No it says the correct answer is 10 :(

Answer 6

I did the exact same thing too, I really have no idea why it says 10 but since 20N is wrong, so we tried doing something else, in the end me and somy got 11.54N

Answer 7

Oh you know what...just read the question more carefully I have an answer. The rod is being supported on two sides: on one side by the hinge and on the other side by the applied force. Therefore each of these points is effectively supporting HALF the weight of the rod, or 5 N each.

This means the applied force is half of what I said earlier: F = 5/sin30 = 10 N

Always read the question...

Answer 8

But here is my question though; how'd you know you have to exactly half the weight?

Answer 9

Well on one hand it's a bit intuitive - it makes sense that both ends would support the same weight. But if you want to math it out...

Say there was no applied force, and all you had was the hinge. The rod would swing down, but it wouldn't fall to the ground - it's being held up by the hinge. This means the hinge must be exerting 10 N of force upward on the rod to balance gravity.

Now say you start applying that force to the other end of the rod. As you increase your applied force, the rod pivots away from the wall. The hinge exerts less and less upward force, while your applied force exerts more and more. Now say the your applied force is so great that you've actually swung the rod all the way around so that it's pointing up from the hinge. At this point, the hinge is exerting 0 N of force on the rod, but your applied force is exerting all 10 N.

When your rod is horizontal, you're halfway between the hinge applying all 10 N, and your vertical applied force applying all 10 N. Therefore each is contributing equally to holding the rod up.

Answer 10

hmmm i do get it, but what else is holding it? i mean one side its the wall and what about the other side?

Answer 11

Ooh ok so that means Im applying the force in such a way that it will not literally point completely upwards but stay horizontal and this means it should be less that the weight because the hinge is also playing a role...did I get that right?

Answer 12

Sorry I forgot to add that when I say "should be less" meaning the applied force

Answer 13

Yup! What I was talking about above was if you're applying a direct vertical force. But that could just as easily be the vertical component of a diagonally-applied force (which is the question here).

Answer 14

lol you know what Im thinking of it as?
it's like this if I have a load buch of dishes to do but I have a friend to help me out.
then why waste all my energy and just do a 50, 50 lmao
xD

Answer 15

but yea it makes sense now haha
thanks @matt101 :)

Answer 16

@KL-RC dream on lol ahahah you have no power here lmao lolthatsme

Answer 17

i didn't really get it but she's explaining it to me @matt101