# A heavy wooden plank is placed so 1/3 of its length protrudes from the side of a pirate ship?

A heavy wooden plank is placed so 1/3 of its length protrudes from the side of a pirate ship. The plank has a total length of 12m and total weight of 120kg. How far onto the plank can a person weighing 100kg walk before the plank tips into the ocean?

Thanks,

### 3 Answers

- oubaasLv 73 weeks ago
overhanging lenght L = 13/3 = 4 m

4^2*120/(12*2)+100*x = 8^2*120/(12*2)

x = (64-16)*120/(24*100) = 240/100 = 2.4 m

- Andrew SmithLv 73 weeks ago
The centre of mass of the plank is at the half way point. 6 m from either end and 2 m to the left of the deck edge.

The torques add to zero at the point of tipping ie 120 * 2 - 100 * x =0

x = 2.4 m to the right of the edge of the deck.

- Anonymous3 weeks ago
until the weight of the person and the plank portion over the gunnel exceed the weight of the plank on the deck. Plus if the ship rolls that might also shift the plank overboard.