Help with torque problem please

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Once I added that in, the answer was correct. In summary, the question asks for the angular acceleration of a uniform horizontal rod when a 4.8 N force at an angle of 63° to the horizontal is applied to one end of the rod. The moment of inertia of the rod is given by I =(m ℓ^2) /12 and the acceleration of gravity is 9.8 m/s^2. Using the equations for torque and sum of torques, the resulting angular acceleration was found to be 2.1821 rad/s^2. However, this answer was incorrect due to the omission of the torque caused by gravity. Once this was added in, the correct answer was obtained.
  • #1
luckysword12
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Homework Statement


A uniform horizontal rod of mass 2.8 kg and
length 2.1 m is free to pivot about one end
as shown. The moment of inertia of the rod
about an axis perpendicular to the rod and
through the center of mass is given by I =(m ℓ^2) /12

If a 4.8 N force at an angle of 63◦
to the horizontal acts on the rod as shown, what is the
magnitude of the resulting angular acceleration about the pivot point? The acceleration
of gravity is 9.8 m/s^2
.
Answer in units of rad/s^2


Homework Equations


Sum of the torques = I * a
Torque = R * F * sin(theta)

The Attempt at a Solution



Here is what I have so far:

(sum of the torques) = (Torque of force F)
I * a = R * F * sin(63)
a = (R * F * sin(63)) / I

I = (M * L^2)/3 (It is rotating at its endpoint not at its center of mass)

a = (3 *(R * F * sin(63))) / (M * L^2)
a = (3 *(2.1 * 4.8 * sin(63))) / (2.8 * 2.1^2)
a = 2.1821 rad/s^2 <-----But this answer is incorrect. Where did I go wrong?

 
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  • #2
Sorry if you came to this but I just figured it out. I forgot the torque due to gravity
 

What is torque?

Torque is a measure of the twisting force on an object. It is a vector quantity, meaning it has both magnitude and direction.

How is torque calculated?

Torque is calculated by multiplying the force applied to an object by the distance from the axis of rotation to the point where the force is applied.

What is the unit of torque?

The unit of torque is Newton-meters (Nm) in the SI system. In the imperial system, it is measured in foot-pounds (ft-lb).

What factors affect torque?

The magnitude of torque is affected by the force applied, the distance from the axis of rotation, and the angle at which the force is applied. Additionally, the type of material and shape of the object can also affect torque.

How is torque used in real-life applications?

Torque is used in many real-life applications, including engines, motors, and tools. It is also important in sports, such as in the rotation of a baseball or the spinning of a gymnast on the uneven bars.

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