- #1
physicsgirl4
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Find mom of inertia and frictional torque
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SUMMARY
The discussion focuses on calculating the moment of inertia and frictional torque of a wheel subjected to an external torque of 60 N·m for 12 seconds, resulting in an angular velocity of 800 revolutions per minute. The moment of inertia is determined to be 27 kg·m², although the calculation requires consideration of frictional torque. The equations used include net torque relationships and angular acceleration conversions, emphasizing the need for correct unit application in angular motion.
PREREQUISITES- Understanding of angular motion and torque concepts
- Familiarity with moment of inertia calculations
- Knowledge of angular acceleration and its units
- Ability to manipulate equations involving torque and angular velocity
- Study the relationship between net torque and frictional torque in rotational dynamics
- Learn how to convert angular velocity from revolutions per minute to radians per second
- Explore the implications of friction in rotational motion and its calculation
- Investigate advanced topics in rotational kinematics and dynamics
Physics students, educators, and anyone involved in mechanical engineering or dynamics who seeks to deepen their understanding of rotational motion and torque calculations.
- #2
I like Serena
Science Advisor
Homework Helper
MHB
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Welcome to PF, physicsgirl4! 
That's the right value!
But the wrong unit...
You converted revolutions to radians, and it's an angular acceleration instead of a angular velocity.
The unit should be rad/s2.
You seem to have lost a pi here...
But the value is not correct yet anyway, since you haven't taken friction into account yet.
Let's set up the equations first:
In the first stage:
$$T_{net} = T_{ext} - T_{fric} = I \cdot \alpha_1$$
$$T_{ext} = 60 N m$$
$$\alpha_1 = {800 \cdot 2\pi \over 60 \cdot 12} {rad \over s^2}$$
In the second stage:
$$- T_{fric} = I \cdot \alpha_2$$
$$\alpha_2 = - {800 \cdot 2\pi \over 60 \cdot 100} {rad \over s^2}$$
This is a set of equations, can you solve it?
physicsgirl4 said:
That's the right value!
But the wrong unit...
You converted revolutions to radians, and it's an angular acceleration instead of a angular velocity.
The unit should be rad/s2.
You seem to have lost a pi here...
But the value is not correct yet anyway, since you haven't taken friction into account yet.
Let's set up the equations first:
In the first stage:
$$T_{net} = T_{ext} - T_{fric} = I \cdot \alpha_1$$
$$T_{ext} = 60 N m$$
$$\alpha_1 = {800 \cdot 2\pi \over 60 \cdot 12} {rad \over s^2}$$
In the second stage:
$$- T_{fric} = I \cdot \alpha_2$$
$$\alpha_2 = - {800 \cdot 2\pi \over 60 \cdot 100} {rad \over s^2}$$
This is a set of equations, can you solve it?