Video: Rotational Inertia With a Weighted Rod Watch the video and then answer the following questions.
Part A Is it easier to balance a long rod with a mass attached to it when the mass is closer to your hand or when the mass is farther away?
Hint 1. Review a specific part of the video. Watch the video again. View the demonstration that Dr. Hewitt has the student perform.
ANSWER: It is easier when the mass is closer to your hand. It is equally easy in both cases. It is easier when the mass is farther from your hand.
Correct Part B How does the rotational inertia of the rod with the mass toward the bottom compare with the rotational inertia of the mass toward the top?
Hint 1. Rotational inertia and balance point Rotational inertia depends on how far the mass is from the balance point.
ANSWER: The rotational inertia of the rod with the mass closer to the top is greater than the rotational inertia of the rod with the mass closer to the bottom. The rotational inertia of the rod with the mass closer to the top is equal to the rotational inertia of the rod
Part B How does the rotational inertia of the rod with the mass toward the bottom compare with the rotational inertia of the mass toward the top?
Hint 1. Rotational inertia and balance point Rotational inertia depends on how far the mass is from the balance point.
ANSWER: The rotational inertia of the rod with the mass closer to the top is greater than the rotational inertia of the rod with the mass closer to the bottom. The rotational inertia of the rod with the mass closer to the top is equal to the rotational inertia of the rod with the mass closer to the bottom. The rotational inertia of the rod with the mass closer to the bottom is greater than the rotational inertia of the rod with the mass closer to the top.
Correct
Part C Why does the rotational inertia of the rod with the attached mass closer to y our hand compare the way it does wit h the rotational inertial of the rod with the attached mass farther away?
Hint 1. Rotational inertia and mass distribution Rotational inertia has to do with how far the mass is from the point of rotation. The farther the mass is from the point of rotation, the greater the rotational inertia.
ANSWER: Rotational inertia depends on whether the mass is farther or closer to the point of rotation. The closer the mass is, the higher the rotational inertia. Rotational inertia depends on whether the mass is lower or higher. Objects where the mass is higher have a greater rotational inertia. Rotational inertia depends on whether the mass is farther or closer to the point of rotation. The farther the mass is, the higher the rotational inertia.
Correct
Part D Is it easier for a circus performer to balance a long rod held vertically with people hanging off the other end, or the same long rod without the people at the other end, and why?
Hint 1. Mass distribution, rotational inertia, and tendency to tip over (rotate) In which of the cases is the rotational inertia reater? ANSWER: It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is smaller.
ANSWER: It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is smaller. It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is greater. It is easier for the performer to balance a long rod held vertically without people at the other end because the rotational inertia is greater. It is easier for the performer to balance a long rod held vertically without people at the other end because the rotational inertia is smaller.
Correct
Video: Difference Between T orque and Weight Watch the video and then answer the following questions.
Part A Where is the center of gravity of the broom that Dr. Hewitt holds up?
Hint 1. Center of gravity and the balance point The center of gravity is at the point where the broom is balanced.
ANSWER: at the center of the heavier side of the broom at the balance point at the center of the broom
Correct
at the center of the heavier side of the broom at the balance point at the center of the broom
Correct
Part B When Dr. Hewitt cuts the broom right through the center of gravity, how do the weights of the two sides of the broom compare?
Hint 1. Center of gravity and weight distribution If the weights were equal, the center of gravity would be in the center of the broom. Is this the case? If not, and the center of gravity is thus closer to one side, then which side will be heavier?
ANSWER: The longer side (the handle) has a greater weight than the bristle side. Both sides of the broom on either side of the center of gravity have equal weight. The shorter side, where the bristles of the broom are, has a greater weight than the handle.
Correct
Part C How does the torque due to the weight of one side of the broom exerted around the balance point compare with the torque exerted by the weight of the other side of the broom around the balance point?
Hint 1. Net torque around balance point When Dr. Hewitt holds the broom by supporting it under its balance point, does the broom rotate? So, what is the net torque due the two sides around the balance point?
ANSWER: The torque due to the weight of the shorter side (the bristles of the broom) is larger in magnitude than the torque due to the weight of the longer side (the handle), and opposite in direction. The torque due to the weight of the shorter side (the bristles of the broom) is smaller in magnitude than the torque due to the weight of the longer side, and opposite in direction. The torque due to the weight of the shorter side (the bristles of the broom) is equal in magnitude to the torque due to the weight of the longer side, and opposite in direction.
Correct
Video Tutor: Balancing a Meter Stick First, launch the video below. You will be asked to use your knowledge of physics to predict the outcome of an experiment. Then, close the video window and answer the question at right. You can watch the video again at any point.
Video Tutor: Balancing a Meter Stick First, launch the video below. You will be asked to use your knowledge of physics to predict the outcome of an experiment. Then, close the video window and answer the question at right. You can watch the video again at any point.
Part A Suppose we replace the mass in the video with one that is four times heavier. How far from the free end must we place the pivot to keep the meter stick in balance?
Hint 1. How to approach the problem. For the meter stick to be in equilibrium, the net torque on it must be zero. Torques about the fulcrum may be exerted by the mass hanging from the end of the stick and by the stick’s own weight. Use the condition that the net torque must be equal to zero to obtain a relationship involving 1) the distance between the left end of the stick and the fulcrum and 2) the distance between the center of mass of the stick and the fulcrum. These two distances must add up to a constant. You should get two equations that you can solve for the location of the fulcrum.
ANSWER: 10 cm 50 cm (in the middle) 75 cm (25 cm from the weight) 90 cm (10 cm from the weight) 25 cm
Correct
Video Tutor: Walking the plank First, launch the video below. You will be asked to use your knowledge of physics to predict the outcome of an experiment. Then, close the video window and answer the question at right. You can watch the video again at any point.
Part A In the video, the torque due to the mass of the plank is used in the calculations. For this question, ignore the mass of the board. Rank, from largest to smallest, the mass needed to keep the board from tipping over. To rank items as equivalent, overlap them.
Hint 1. How to approach the problem In equilibrium, the sum of the clockwise torques about an axis must equal the sum of the counterclockwise torques.
ANSWER:
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Correct
4/7/13
Lab 8 (Rotational Motion)
Score Summary:
4/7/13
Lab 8 (Rotational Motion)
Score Summary: Your score on this assignment is 62.3%. You received 2.49 out of a possible total of 4 points.
session.masteringphysics.com/myct/assignmentPrintView?assignmentID=2228372
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