Gravitational torque about a point on a rod

In summary, the conversation discusses the calculation of gravitational torque on a 2.0 kg uniform rod that is 1 m in length and positioned horizontally. The point A, located 25 cm from the left end of the rod, is used as the reference point. The formula T=Fr is mentioned, with F=mg. The center of gravity of the rod is identified as being directly at its center, 25 cm from point A. The individual's calculation of the torque results in 3.675 N*m, but the answer in the book is -2.1 N*m. The individual questions the accuracy of the book's answer and requests assistance in identifying where their calculation may have gone wrong.
  • #1
cdbowman42
14
0
1. A 2.0 kg uniform, horizontal rod is 1 m in length. What is the gravitational torque about the point A that is 25 cm from the left end of the rod.


2. T=Fr
F=mg
T=mgr


3. The center of gravity of the rod is directy at its center, so is therefore 25 cm from the point A. I thought the torque would be the product of the amount of mass on that side of the center of gravity (3/4 or the 2 kg rod since it is uniform), acceleration due to gravity, and the distance of the point to to center of gravity. The answer in the back of the book says -2.1 N*m (Assuming clockwise motion is negative), but I get 3.675 N*m. Where am I going wrong?
 
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  • #2
The book's answer would appear to be incorrect. Then again, so does yours! :smile:

Something's gone awry in your calculations. Perhaps you should present them in detail.
 

FAQ: Gravitational torque about a point on a rod

What is gravitational torque about a point on a rod?

Gravitational torque is the twisting force exerted on an object due to the gravitational pull of another object. When considering a rod, the gravitational torque about a point on the rod is the torque exerted on that point due to the gravitational force acting on the entire rod.

How is gravitational torque calculated?

Gravitational torque about a point on a rod can be calculated by multiplying the mass of the rod by the distance from the point to the center of mass of the rod, and then multiplying that by the force of gravity acting on the rod.

What factors affect gravitational torque on a rod?

The factors that affect gravitational torque on a rod include the mass of the rod, the distance from the point to the center of mass of the rod, and the force of gravity acting on the rod. Additionally, the angle at which the rod is positioned relative to the direction of gravity can also affect the gravitational torque.

How does gravitational torque affect the stability of a rod?

Gravitational torque can affect the stability of a rod by causing it to rotate around a point if the torque is greater than the resistance of the rod. This can lead to the rod toppling over if the torque is not balanced by another force.

Can gravitational torque be negative?

Yes, gravitational torque can be negative. This occurs when the direction of the gravitational force is opposite to the direction of rotation, resulting in a negative torque value. Negative torque can cause an object to rotate in the opposite direction as positive torque.

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