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Ch 10: Dynamics of Rotational Motion

Chapter 10, Problem 10

A metal bar is in the xy-plane with one end of the bar at the origin. A force F = 97.00 N)i + (-3.00 N)j is applied to the bar at the point x = 3.00 m, y = 4.00 m. (a) In terms of unit vectors i and j, what is the position vector r for the point where the force is applied?

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welcome back everybody. We are looking at a wrench in a wheel nut from a top down view in the X. D. Planes. I'm actually gonna draw out our XZ plane right now. Here is our X. And we have ours just like that And let me label it such at the origin is our nut. And we have our wrench exerting a force to this nut. Now we are told at the point negative one in 10.25 -1 in the X. direction. .25 in direction. We have some force given by this equation right here. So it looks like in the extraction is a little bit bigger. So our forces gonna look something like this. And we are asked to find what the position vector is from the origin to the point of our application of our force. So find our well our is going to have the form of some X. Value in the times ri unit. So along the X axis essentially plus some Z coordinate. I'm our K. Unit vector which means to direction. Well for this X and z we can actually just use the point of application coordinates. So let's go ahead and plug those in. We have that our position vector is equal to negative one times our I unit vector plus 0.25 times our K. Unit vector. I just want to point this out here. Although we were given this force. This was just a red herring here. We didn't have to use that at all to find our position vector of native one. I plus 10.25 K, corresponding to our final answer choice of D. Thank you guys so much for watching. I hope this video helped. We will see you all in the next one.
Related Practice
Textbook Question
A machinist is using a wrench to loosen a nut. The wrench is 25.0 cm long, and he exerts a 17.0-N force at the end of the handle at 37° with the handle (Fig. E10.7). (b) What is the maximum torque he could exert with this force, and how should the force be oriented?

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Textbook Question
A metal bar is in the xy-plane with one end of the bar at the origin. A force F = 97.00 N)i + (-3.00 N)j is applied to the bar at the point x = 3.00 m, y = 4.00 m. (b) What are the magnitude and direction of the torque with respect to the origin produced by F?
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Textbook Question
A large wooden turntable in the shape of a flat uniform disk has a radius of 2.00 m and a total mass of 120 kg. The turntable is initially rotating at 3.00 rad/s about a vertical axis through its center. Suddenly, a 70.0-kg parachutist makes a soft landing on the turntable at a point near the outer edge. (a) Find the angular speed of the turntable after the parachutist lands. (Assume that you can treat the parachutist as a particle.)
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Textbook Question
The Spinning Figure Skater. The outstretched hands and arms of a figure skater preparing for a spin can be considered a slender rod pivoting about an axis through its center (Fig. E10.43). When the skater's hands and arms are brought in and wrapped around his body to execute the spin, the hands and arms can be considered a thinwalled, hollow cylinder. His hands and arms have a combined mass of 8.0 kg. When outstretched, they span 1.8 m; when wrapped, they form a cylinder of radius 25 cm. The moment of inertia about the rotation axis of the remainder of his body is constant and equal to 0.40 kg•m2 . If his original angular speed is 0.40 rev/s, what is his final angular speed?

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