# Centre of mass of of an isosceles Triangle

## Homework Statement

Hi
I am really stuck on this problem. It reads as such:
A uniform triangular lamina is isocceles and has the line y= 4 as its axis of symmetry. One of the vertices of the triangle is the point (2,1). Given that the x-co-ordinate of the centre of mass of the lamina is -3, find the co-ordinates of the other two vertices.

I am not sure where to begin. Any hints or guides please?

## Homework Equations

Centre of mass = (X1 +x2+X3/3, Y1+Y2+Y3/2)

## Answers and Replies

vela
Staff Emeritus
Science Advisor
Homework Helper
Education Advisor
Try starting with a sketch.

Try starting with a sketch.
Thanks. I will commence ze sketch!

supratim1
Gold Member
the Y-coordinate of COM will be 4, as it will lie on y=4, the axis of symmetry. now proceed. one of the vertices will be the reflection of (2,1) on y=4. the third one will lie on y=4, just find the x coordinate of that.

the Y-coordinate of COM will be 4, as it will lie on y=4, the axis of symmetry. now proceed. one of the vertices will be the reflection of (2,1) on y=4. the third one will lie on y=4, just find the x coordinate of that.
Let me try it. Thanks!

supratim1
Gold Member
Let me try it. Thanks!

welcome...so did it work?

welcome...so did it work?
Sorry! I will let you know tonight. I have 5 exams between now and monday. All A2! Cheers!

supratim1
Gold Member
ok..all the best!