00:03Welcome, in this video we are going to solve exercise 4.1, which tells us, a tractor of
00:09A 2100-pound load is used to lift 900 pounds of gravel. Determine the reaction forces at the loads.
00:15Rear tires a, b, front tires b. To solve this we have to take into account that they are
00:21two tires of a, b, series a four existing tires on the tractor, now something important a
00:26What to keep in mind is when a moment is positive, and when a moment is negative, remembering that the
00:31Momentum is force times distance, this equals momentum, everything that goes with the hands of the clock
00:36Clockwise is in the negative direction, and everything that goes against the hands of the clock is in the negative direction.
00:41positive, then we have the reaction r sub a x, and the reaction r sub a y, now, what we are going to
00:47to do
00:48It's the sum of moments, to find that force, and then we perform the sum of forces
00:53in y, and we have the result, in this case, we are going to do the sum of forces in b, in the
00:59moment
00:59At point b, the mechanical shovel's force goes downwards; at point b, the rotation distance
01:04From point b, and the force of the mechanical blade in its rotation with a negative direction, we now do,
01:10The sum of moments at b equals zero, that is equal to minus 900 pounds per 50 inches,
01:16plus 2100 pounds per 40 inches, minus twice the reaction at r sub a y, this is because there exists
01:23two tires, in said reaction, by 60 inches, this equals zero, solving us
01:28gives, minus 45000, plus, 84000, minus twice the reaction at a and, for 60 inches equals
01:36At zero, this gives us 39000, minus the reaction at a and, times 60 inches, equal to zero, we get
01:43The result in the reaction to y is 325 pounds, now we have 2100 pounds which is the weight
01:50of the tractor, located at point g, then the rotation is to the right with respect to
01:54to point b, by the distance of this rotation, so this is in the positive direction, now
02:00We perform the summation of forces in y, this equals zero, so it is double, therefore
02:05The 325 pounds, since we take the two tires as a reference, minus 2100, this is the weight of the
02:12tractor, and more, ra sub and, the reaction, we obtain, minus 2350 minus twice the reaction in
02:19And, resulting in 1175 pounds, well that's all, if you think it was useful to you, don't
02:26Don't forget to subscribe.
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