00:01
We're told the hydraulic system of backhoe is used to lift a load as shown in figure 11 .48.
00:08
So i've reproduced the backhoe here.
00:13
There's a force from the hydraulic system acting here.
00:17
That's a distance l1 from our pivot point at a.
00:21
There's the weight of the arm, which acts through its center of mass.
00:25
That's a distance l2 from a.
00:27
And then there's the weight of the payload in the bucket that.
00:32
That acts at a distance l3 from the pivot point.
00:39
The point at a is fixed, so the sum of the moments about that point is zero, and if we take count and clockwise as positive, we wind up with our moment balance is the force from the hydraulic system times l, and the force from the hydraulic system acts perpendicular to the moment arm.
01:02
The weight and the load do not act perpendicular.
01:08
So we need to take the component that is perpendicular by taking the sign of this angle.
01:16
So we get the weight of the arm times the sign of that angle is the component in this direction times l2.
01:23
It's in the clockwise direction so we have a minus sign...