13. [-/10 Points] DETAILS SERPSE10 10.5.P.019.CTX. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Your grandmother enjoys creating pottery as a hobby. She uses a potter's wheel, which is a stone disk of radius R = 0.520 m and mass M = 100 kg. In operation, the wheel rotates at 60.0 rev/min. While the wheel is spinning, your grandmother works clay at the center of the wheel with her hands into a pot-shaped object with circular symmetry. When the correct shape is reached, she wants to stop the wheel in as short a time interval as possible, so that the shape of the pot is not further distorted by the rotation. She pushes continuously with a wet rag as hard as she can radially inward on the edge of the wheel and the wheel stops in 6.00 s. (a) You would like to build a brake to stop the wheel in a shorter time interval, but you must determine the coefficient of friction between the rag and the wheel in order to design a better system. You determine that the maximum pressing force your grandmother can sustain for 6.00 s is 65.0 N. HK = (b) What If? If your grandmother instead chooses to press down on the upper surface of the wheel a distance / = 0.200 m from the axis of rotation, what is the force (in N) needed to stop the wheel in 6.00 s? Assume that the coefficient of kinetic friction between the wet rag and the wheel remains the same as before. (Enter the magnitude.) N Need Help? Read it 14. [-/10 Points] DETAILS SERPSE10 10.6.OP.018. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A rectangular sheet of plywood is attached to a vertical support by a set of hinges. Assume the sheet is uniform and has height 2.15 m, width 0.850 m, and mass 22.5 kg. (a) Determine its moment of inertia (in kg . m ) for rotation on its hinges. kg . m2 (b) Are any pieces of data unnecessary? (Select all that apply.) O The width of the sheet is unnecessary. O The mass of the sheet is unnecessary. The height of the sheet is unnecessary. O No; all of the data are necessary. Need Help? Read It 15. [-/0 Points] DETAILS SERPSE10 10.6.P.024. MY NOTES ASK YOUR TEACHER Two balls with masses M and m are connected by a rigid rod of length & and negligible mass as shown in the figure below. (Submit a file with a maximum size of 1 MB.) (a) For an axis perpendicular to the rod, show that the system has the minimum moment of inertia when the axis passes through the center of mass. (b) Show that this moment of inertia is I = UL?, where u = mM/(m + M). This answer has not been graded yet. Need Help? Read It16. [-/10 Points] DETAILS SERPSE10 10.6.OP.020. MY NOTES ASK YOUR TEACHER In the figure below, three thin rods are all connected at their centers. The rods each have the same length L and mass m, and they are all perpendicular to one another. Each rod lies on one of the x, y, or z-axes as shown. The entire structure formed by the rods is rotated about an axis that is parallel to the y-axis and passes through the end of the rod that lies on the x-axis. What is the moment of inertia of this structure about the axis of rotation? (Use any variable or symbol stated above as necessary.) Axis of rotation Need Help? Read It 17. [-/10 Points] DETAILS SERPSE10 10.7.P.025. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Rigid rods of negligible mass lying along the y axis connect three particles. The system rotates about the x axis with an angular speed of 3.90 rad/s. 4.00 kg y= 3.00 m O 2.00 kg Oy = -2.00 m 3.00 kgy = -4.00 m (a) Find the moment of inertia about the x axis. kg . m2 (b) Find the total rotational kinetic energy evaluated from - Ic2. (c) Find the tangential speed of each particle. 4.00 kg particle m/s 2.00 kg particle m/s 3.00 kg particle m/s (d) Find the total kinetic energy evaluated from __1m v.2. (e) Compare the answers for kinetic energy in parts (b) and (d). This answer has not been graded yet. Need Help? Read It Watch It