Physics - Moments Question

Your working is correct. But let's not forget that the string is anchored to the shelf 0.3m away.
Therefore it is not

\frac{A}{\sin 30}

, it is the counterclockwise moment of

\frac{A}{0.3\sin 30}

Which will yield 51N :smile:

Reply 2

OP

Original post by The-Spartan

Your working is correct. But let's not forget that the string is anchored to the shelf 0.3m away.
Therefore it is not

\frac{A}{\sin 30}

, it is the counterclockwise moment of

\frac{A}{0.3\sin 30}

Which will yield 51N :smile:

Thanks for the reply :smile:

I sort of understand why you did *0.3 but I don't know why you did it to the sin(30)?
I thought the force acting on A would just be trig and not involve the 0.3? I'm still a bit confused! Sorry if I sound stupid! I just suck at the mech part of phys :frown:

Reply 3

Original post by CrazyFool229

Thanks for the reply :smile:

I sort of understand why you did *0.3 but I don't know why you did it to the sin(30)?
I thought the force acting on A would just be trig and not involve the 0.3? I'm still a bit confused! Sorry if I sound stupid! I just suck at the mech part of phys :frown:

Here, ill draw a diagram for you just a sec, ill edit this in a min.
And no you dont sound stupid at all! its not easy stuff! :biggrin:

(edited 7 years ago)

Reply 4

OP

Original post by The-Spartan

Here, ill draw a diagram for you just a sec, ill edit this in a min.
And no you dont sound stupid at all! its not easy stuff! :biggrin:

Wow thanks for that. Much appreciated :biggrin:

So just to clarify, is the clockwise moment A the dotted arrow going upwards then?

Reply 5

TheTechnoGuy

8

This looks like a question from one of the Physics specimen papers. Nice

Reply 6

Original post by CrazyFool229

Wow thanks for that. Much appreciated :biggrin:

So just to clarify, is the clockwise moment A the dotted arrow going upwards then?

No worries :smile:

The clockwise moment is the one you found yourself. You labelled this A so i did too, maybe you have anticlockwise and clockwise mixed up?

The anti-clockwise moment is the dotted line, acting upwards. This is

T(0.3\sin{30})

.

Reply 7

OP

Original post by TheTechnoGuy

This looks like a question from one of the Physics specimen papers. Nice

Yup, it is. Just got round to finishing all the questions but I had to go back to this one because I couldn't get anywhere near 50N! Turns out it was that one silly step with the *0.3 :frown:

Reply 8

OP

Original post by The-Spartan

No worries :smile:

The clockwise moment is the one you found yourself. You labelled this A so i did too, maybe you have anticlockwise and clockwise mixed up?

The anti-clockwise moment is the dotted line, acting upwards. This is

T(0.3\sin{30})

.

Yep, my bad again getting it mixed up haha. Thanks a lot for your help btw! :biggrin:

Reply 9