A person holds a ladder horizontally at its center. Treating the ladder as a uniform rod of length 4.15 m and mass 7.98 kg, find the torque the person must exert on the ladder to give it an angular acceleration of 0.396 rad/s2.

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Answer:

4.535 N.m

Explanation:

To solve this question, we're going to use the formula for moment of inertia

I = mL²/12

Where

I = moment of inertia

m = mass of the ladder, 7.98 kg

L = length of the ladder, 4.15 m

On solving we have

I = 7.98 * (4.15)² / 12

I = (7.98 * 17.2225) / 12

I = 137.44 / 12

I = 11.45 kg·m²

That is the moment of inertia about the center.

Using this moment of inertia, we multiply it by the angular acceleration to get the needed torque. So that

τ = 11.453 kg·m² * 0.395 rad/s²

τ = 4.535 N·m

The Torque will be "4.535 N.m".

Given:

Mass of ladder,

  • m = 7.98 kg  

Length of ladder,

  • L = 4.15 m

The moment of inertia will be:

→ [tex]I = \frac{mL^2}{12}[/tex]

     [tex]= \frac{7.98\times (4.15)^2}{12}[/tex]

     [tex]= \frac{7.98\times 17.2225}{12}[/tex]

     [tex]= 11.45 \ kg.m^2[/tex]

hence,

The torque will be:

→ [tex]\tau = 11.453\times 0.395[/tex]

      [tex]= 4.535 \ N/m[/tex]

Thus the above approach is correct.      

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