A square metal plate 2.5m on each side is pivoted about an axis though point O at its center and perpendicular to the plate. Calculate the net torque due to the three forces if the magnitudes of the forces are F1=18N, F2=20N, and F3=11N..

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Complete Question

The diagram for this question is shown on the first uploaded image

Answer:

The net torque  [tex]\tau = 21.95N \cdot m[/tex]

Explanation:

   From the question we are told that

      The length of each side is  [tex]L = 2.5 m[/tex]

       The first force is  [tex]F_1 = 18N[/tex]

        The second force is  [tex]F_2 = 20 N[/tex]

         The third force is [tex]F_3 = 11N[/tex]

The free body diagram for the question is shown on the second uploaded image

  Generally torque is mathematically represented as

       [tex]\tau = r * F[/tex]

 Where [tex]\tau[/tex] is the torque

             r is  the length from the rotating point to the point the force is applied, this is also the radius of the circular path made

             F is the force causing the rotation.

looking at the free body diagram we can deduce that L is the diameter of the circular path made as a result of toque

       Now  for the torque due to force [tex]F_1[/tex]

               [tex]\tau_1 = - F_1 * r_1[/tex]

The negative sign is because the direction of  [tex]F_1[/tex]  is clockwise

     =>  [tex]\tau_1 = - F_1 * \frac{L}{2}[/tex]

Substituting value

           [tex]\tau_1 = - 18 * \frac{2.5}{2 }[/tex]

            [tex]\tau_1 = - 22.5 N \cdot m[/tex]

The torque as a result of the second force is  mathematically evaluated as

            [tex]\tau_2 = F_2 * r_2[/tex]

            [tex]\tau_2 = F_2 * \frac{L}{2}[/tex]

                [tex]= 20 * \frac{2.5}{2}[/tex]

                 [tex]\tau_ 2 = 25 \ N \cdot m[/tex]

The torque as a result of the third  force is  mathematically evaluated as

            [tex]\tau_3 =r_3 (F_3 sin \theta + F_3 cos \theta )[/tex]

            [tex]\tau_3 = \frac{L}{2} (F_3 sin \theta + F_3 cos \theta )[/tex]

Where the free body diagram [tex]\theta = 45^o[/tex]

                [tex]\tau_3 = \frac{2.5}{2} (11 * sin (45) +11 cos (45) )[/tex]

                 [tex]\tau_ 3 = 19.45 \ N \cdot m[/tex]

The net torque the mathematically

       [tex]\tau = \tau_1 + \tau_2 + \tau_3[/tex]

substituting value

       [tex]\tau = -22.5 + 25 + 19.45[/tex]  

           [tex]\tau = 21.95N \cdot m[/tex]

 

     

     

           

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