How do I rotate arrowhead to point vertically upward?

[Alexandros81]

Hi.

I am drawing this free body diagram for a problem in Physics-Dynamics.

FBD P14_6.svg
(5.93 kB . 105x148)
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As you can see the arrowhead for the vertical line is pointing to the right.
I want to be pointing upwards.

Also I will be drawing a line with arrowhead down to the left.

[Moini]

The vertical line is not vertical at the end. Please remove the duplicate node.