Calculating Moment of Force on Bicycle Pedal

[Googl]

Hi,

I have a practice question. I have managed to calculate part of it and one last bit I haven't been able to. Hoping you can give me some ideas.

I am given a bicycle pedal that is a some distance long and has been pushed downwards by a given force. Here I have been able to calculate the moment of force when the crank is horizontal but not when the crack us turned a certain degrees below the horizontal.

 

[sophiecentaur]

Horizontal distance from pedal to crankshaft is the distance you need.

 

[Googl]

Horizontal distance from pedal to crankshaft is the distance you need.

So, the moment of force will remain the same no matter when the crack has been turned 65 degree below the horizontal?

 

[sophiecentaur]

Yes it will. The horizontal distance from the force of your weight gets less and less as the crank goes from the horizontal, 'till it gets to zero when you are at the bottom.
taking the angle from the horizontal, the moment will be W L cos(angle).

 

[Doc Al]

Yes it will.

I think you meant "No it won't."

 

[sophiecentaur]

Oh no it won't/ Oh yes it will. Durrr
I may be sleepy but the maths is correct! and no it won't. (Thanks)

 

[Googl]

Yes it will. The horizontal distance from the force of your weight gets less and less as the crank goes from the horizontal, 'till it gets to zero when you are at the bottom.
taking the angle from the horizontal, the moment will be W L cos(angle).

Thanks for the help.

What does W and L stand for?

 

[decepticon_BE]

W-the Weight or Force acting
L- IS the distance through which it acts at
cos (0) - the angle through L the weight is acting

 

[sophiecentaur]

What does W and L stand for?

If you want to learn about these things it's a good idea to read Wikipedia etc. and not just rely on these answers. Self help is good for you, which is why you often get 'partial' answers on this forum, initially.

 

[Googl]

If you want to learn about these things it's a good idea to read Wikipedia etc. and not just rely on these answers. Self help is good for you, which is why you often get 'partial' answers on this forum, initially.

I have a good understanding and I am currently expanding on that knowledge, I am assuming this is why forums exist. I didn't expect to get the real answers just some clues. I study maths mostly W could stand for width and L could stand for length. So you can see my previous need to confirm this.

I actually had an idea for the answer but just wanted to confirm.

 

[sophiecentaur]

Would it be too much to ask you to look up the formula and see just what my two letters could possibly stand for? I thought the cos(angle) was the only thing necessary to point out. Now . . . . what could the other two letters, in your wildest dreams, represent? (Bearing in mind we're discussing Moments.)