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A person carries a plank of wood 2 m long with one hand pushing down on it at one end with a force F1 and the other hand holding it up at 50 cm from the end of the plank with force F2. If the plank has a mass of 20 kg and its center of gravity is at the middle of the plank, what are the forces F1 and F2?

Respuesta :

Answer:

F1= 196 N

F2= 392 N  

Explanation:

Given:

length of the plank = 2 m

mass of the plank = 20 kg

Weight of the plank = 20 x 9.8 =196 N  

Torque due to the weight of the plank with respect to the pivoted end (i.e the end held by the hand) Counter clockwise torque  = 196 x cog of wood

= 196 x 1 = 196 Nm

Clockwise torque = F2 x 0.5

for the balanced case  

F2 x 0.5 = 196  

F2 = 196/ 0.5

F2= 392 N  

now,

the net force

Net downward force  =Net upward force

F1 + weight of plank = F2

F1 + 196 = 392N

F1 = 392 – 196

F1= 196 N