Math Is Fun Forum

ramzel

Member

Registered: 2015-09-04

Posts: 1

Mechanics

Hello can someone help me out with this question.

I am getting 3 variables.

Thanks.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,164

Re: Mechanics

hi ramzel

Welcome to the forum.

Yes, this should happen.  You resolve horizontally and vertically and you'll have two equations and unknowns T (tension) , Q and alpha.

Use

to eliminate alpha.

You'll have an equation with T squared and a more complicated quadratic expression in Q.

To get the minimum T, make T squared the subject and consider how you can make the right hand side of the equation as small as possible.  As the RHS is a quadratic, it's just a case of finding the minimum point on the quadratic ie. what value of Q to make this minimum.

Once you have that you can go back to the two equations with that value for Q, and find the corresponding values for T and alpha.

Hope that helps,

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob