mechanics question - Please help me !

hi can anyone help me with this mechanics question , from june04 phy1 paper.
I got my phy1 exam 2morow :eek:

4. A gardener is trying to remove a tree stump. He has dug away the
soil around it, but it is still anchored by a vertical root at A
and a horizontal root at B.
The gardener pulls horizontally on the top of the stump with a force
of 310 N, but it does not move.

The second diagram shows some of the horizontal forces on the stump.
Force X is the tension in the root at B.
One horizontal force is missing from the diagram.
Add an arrow to a copy of this diagram to represent this force and label it Y. (1)
i got this right, its towards the right next to the letter A in the 2nd diagram

Using the principle of moments, determine force X.
(You should ignore the vertical forces on the tree stump.) (2)

Explain why, in this moments calculation, it is reasonable to ignore the
vertical forces on the stump. (1)

Calculate force Y. (2)

Thanks for any help

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Reply 1

DrJackal

Y would be opposite to B

Clockwise moments = anticlockwise moments

0.160 x X = 310 x 0.950

0.160 x X = 294.5

x = 294.5 / 0.160 = 1840 N

It is reasonable to ignore the vertical forces on the stump because they are approximately acting through A the pivot.

y + 310 = 1840 so y = 1840 - 310 = 1530 N