Lifting 1

[Mustafinho]

I want to find out the force required by a person to lift a 10ft x 20ft board that is on the ground at a 20 degree angle. The board weights about 150 lbs. It is fixed on the ground with one end and holding the higher non-fixed end, I want to know if an average adult can push it up to lets say 24 degree angle. Is there a formula to derive the force needed?

 

[jayrod12]

Yes that is basic statics. The force required would change as the centre of gravity moved closer towards the fixed end however from 20-24 degrees it likely wouldn't be a significant amount.

This is assuming the board in to rigid to deflect under load, i.e. your "fixed" end is actually pinned (free to rotate but fixed from translation) and the board will not bend when lifted.

 

[allgoodnamestaken]

Figure out what what desired end deflection corresponds with your 24 degree angle and the length of your board (trig). Model as a beam with a fixed end, put a unit load at the end you want to deflect and see how much deflection that load causes. Divide deflection wanted by deflection given by unit load to get approximate required force needed at that location to get the deflection required.

Now you also have to check if its possible to have the board deflect that much without failing, etc.

 

[jayrod12]

I'd like to modify my previous answer. If free to rotate at the end, and the person only pushes straight up (not forward as well) then the force would always be exactly half of the board weight.

If the end is truly fixed (not free to rotate) then it is as allgood described.