Suppose a crate of mass 9.4 kg is placed on the plank in the figure below at a d

Question

Suppose a crate of mass 9.4 kg is placed on the plank in the figure below at a distance x = 7.0 m from the left end. If the plank has a mass of 12 kg, find the forces exerted by the two supports on the plank. (Indicate the direction with the sign of your answer.)

O 0/2 points I Previous Answers GioCP2 8.P 027 Suppose a crate of mass 9.4 kg is placed on the plank in the figure below at a distance x 3 7.0 (Indicate the direction with the sign of your answer.) left support right support 7.0 m Im Need Help? Read It Talk to a Tutor Submit Answer Save Progress Practice Another Version

Explanation / Answer

The net force in vertical direction is zero since the system is not accelerating upwards.

R + N - mg - Mg = 0

where R is the normal force exerted by left support and N is the normal force exerted by right support.

R + N = (9.4 + 12)9.8 = 209.72

Also, torque on this system is zero since the system is not rotating in any direction.

So, taking the torque about the left support we get:

9.4(9.8)(x - 3) + 12(9.8)(3) - N(7) = 0

=> 9.4(9.8)(7 - 3) + 12(9.8)(3) - N(7) = 0

=> N = 103.04 Newton

therefore, R = 209.72 - 103.04 = 106.68 Newton.

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