bit o help pwease :)

[Sarahisme]

could i have some help with this question, i just can't quite figure out what to do....

 

 

for part a i said

 

a) a) the torque exerted by the 80N block via T1. The torque exerted by T2. The torque exerted by the side thingy ‘wall’.(i.e. the hinge)

 

but i dunno how to do the next few bits....

 

Sarah

[Sarahisme]

ok ok....hang on....for part b) i am not sure how you 'show' it i'll explain what i think the answer is......

 

lets call downwards the +ve direction.

so the torque exeted by the block is +ve (let it be Torque1)

so Torque 1 = L x 80N

L is the length of the strut

 

since at the other end of the strut there is a hinge, and since the strut has neglible mass (i.e no mass) therefore there are no torques/forces at that end of the strut. and since the system is in equlibrium therefore there has to be an opposite torque exerted on the strut, which can only come from one place, which is from T2. and since it is the vertical force component of T2 that will exert the torque, therefore the vertical component of T2 has to be 80N.

i.e because Torque1 = Torque 2

L x 80N = L x T2y

T2y = 80N

 

lol that was very long winded wasnt it,

[Sarahisme]

for c) if the mass of the strut is negligble, then the force exerted on the strut by hinge should be 0?

[Bob182]

for c) if the mass of the strut is negligble, then the force exerted on the strut by hinge should be 0?

 

If you resolve your forces you will find the answer. The key to these kind of questions is that if the system is static, then the net force in any direction is zero - i.e. they cancel each other out.

 

I suggest looking at the vertical forces and horizontal forces in turn.

[Sarahisme]

what do other people get for part c?

[Sarahisme]

is it a numerical or an anayltical (is that the right word??) answer?

 

i.e. is it numbers of letters?

[Sarahisme]

ok this is what i now get, ignore ALL of my previous answers...

 

i get that...

T2 = 160 N

and that (for part c) the forcee exerted on the strut by the hinge is 138.56 N or 140 N to 2 sig. figures

[Sarahisme]

? ello?

[Primarygun]

have you got it now?

[reverse]

Gee, that’s asking to dig deep down among the disused skills.

 

Umm, as far as I can remember, the trick is to think about an angle (like the angle of the strut/string thingy as not an angle type force at all.

 

But rather think of it as two forces, one horizontal and one vertical.

 

Say you were walking along with two of your friends, one on your left and one on your right.

 

If one pulled you forward and one pushed you sideways then you would move in a angle of about 45 degrees.

 

So that angular movement (vector), can be thought of as the product of two forces rather than just one angular force.

 

0nce you get that idea...the rest will be easy.

 

I think.....(it's been a while).