I was given this solution for this torque problem but I have NO why certain step
ID: 1784209 • Letter: I
Question
I was given this solution for this torque problem but I have NO why certain steps were made. Please tell me what makes this specific torque problem unique from all the others and simplify the steps that I should take to get to the answer as the current solution given is MUCH too vague for me.
10. Two statics problems (15 pts each) (a) A plank of length 8 meters and mass 60 kg sits at rest on two supports as shown below. The mass of the plank is distributed uniformly, and the forces from the supports are vertical. A child of mass 25 kg sits on the plank a distance 2.0 mcters from the left end.-Find the forces of each support on the plank.Explanation / Answer
the plank is in static equilibrium and rotational equilibrium
In rotational equilibrium
net torque about the left end = 0
torque due to the weight of plank Tp = -mp*g*L/2 = -60*9.8*8/2 = -2352 Nm (clockwise)
torque due to the weight of child Tc = -mc*g*2 = -25*9.8*2 = -490 Nm (clockwise)
torque due to the force on right T2 = F2*L (counterclockwise)
net torque = 0
T2 + Tp + Tc = 0
F2*8 - 2352 - 490 = 0
F2 = 355.25 N <<<<-----answer
In static equilibrium
along vertical
net force = 0
F1 + F2 - Wc - Wp = 0
F1 + 355.25 - (25*9.8) - (60*9.8) = 0
F1 = 477.75 N
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