Question

A uniform plank weighing 50N and 12m long is pivoted at a point of 4m from one end.A boy weighing 30N sits on the plank 7m from pivot.Where must his elder brother whose weight is 80N sit to balance the plank horizontally

Answer 1

Draw a free body diagram and set the total moment about the fulcrum/pivot equal to zero. Let x be the distance of the elder brother from the pivot.

80*x = 50*2 + 30*7 = 310 N*m

x = 3.87 m (on the opposite side of the pivot from the 30 N brother)

This location is quite near the edge of the plank

Answer 2

5.00

Answer 3

A uniform plann weighing 50newton and 13meter long is pivoted at a point 4 meter from one end A boy weighing 30newton sit on a plank7 meter from the pivot where must his elder brother whose weight is 80newton sit to balance the plank horizontally

Answer 4

Not correct