
Concept explainers
(a)
To Calculate: The moment of inertia of combination of platform-drum.
(a)

Answer to Problem 82P
The moment of inertia of combination of platform-drum is 1.2 kg⋅m2 .
Explanation of Solution
Given data:
Radius of the concentric drum, R=10 cm
=(10 cm)(1 m100 cm)=0.100 m
Mass of the hanging object, M=2.50 kg
Distance through which the object falls, D=1.80 m
Time, t1=4.2 s
Formula used:
Torque, τ=Iα
Where, I is the moment of inertia and α is the angular acceleration.
From Newton’s second law of motion:
∑Fi=miai
Where, F represents force, m represents mass and a represents acceleration.
Second equation of motion is:
s=v0t+12at2
Where, s is the displacement, t is the time, a is the acceleration and v0 is the initial velocity.
Calculation:
Apply the Newton’s second law of motion to the platform
∑τ=TR =I0α .......(1)
Apply the Newton’s second law of motion to the weight:
∑Fy=Mg−T =Ma .......(2)
Relation between angular acceleration and acceleration is α=aR
Substituting for α in equation (1) then the tension in the string is
T=I0aR2
Now, substituting for the tension in equation (2) , and solve for the moment of inertia,
Mg−I0aR2=Ma I0=MR2(g−a)a=MR2(ga−1) ..........(3)
The relation among the distance, acceleration and time is given by
s=v0t+12at2
The intial velocity (v0) of the object is zero.
Substitute for the initial velocity (v0) of the object and distance in the above equation:
D=12at2a=2Dt2
The moment of inertia of combinaiton of platform-drum is: I0=MR2(gt22D−1) =(2.50 kg)(0.100 m)2((9.80m/s2)(4.20 s)22(1.80 m)−1) =1.18 kg⋅m2 ≈1.2 kg⋅m2
Conclusion:
The moment of inertia of combination of platform-drum is 1.2 kg/m2 .
(b)
To Calculate: The total moment of inertia.
(b)

Answer to Problem 82P
The total moment of inertia is 3.1 kg⋅m2 .
Explanation of Solution
Given data:
Radius of the concentric drum, R=10 cm
=(10 cm)(1 m100 cm)=0.100 m
Mass of the hanging object, M=2.50 kg
Distance fall by the object, D=1.80 m
Time, t2=6.8 s
Formula used:
From the previous part:
Itotal=MR2(gt22D−1)
Calculation:
Substitute the values and solve for total moment of inertia:
Itotal=MR2(gt22D−1) =(2.50 kg)(0.100 m)2((9.80m/s2)(6.80 s)22(1.80 m)−1) =3.1 kg⋅m2
Conclusion:
Total moment of inertia is 3.1 kg⋅m2 .
(c)
To Calculate: The moment of inertia of the object.
(c)

Answer to Problem 82P
The moment of inertia of the object is 1.9 kg⋅m2 .
Explanation of Solution
Given data:
The total moment of inertia is 3.1 kg⋅m2 .
The moment of inertia of combination of platform-drum is 1.2 kg⋅m2 .
Formula used:
The moment of inertia of the object can be calculated by using the formula:
I=Itotal−I0
Calculation:
Moment of inertia of the object, I=Itotal−I0
=3.12 kg⋅m2−1.18 kg⋅m2=1.9 kg⋅m2
Conclusion:
Moment of inertia of the object is 1.9 kg⋅m2 .
Want to see more full solutions like this?
Chapter 9 Solutions
Physics for Scientists and Engineers
- An object is placed 37.4cm in front of a diverging lens with a focal length of 18.1 cm. Please provide your answers in units of cm if necessary. bookmark_border1.0p3a Find the image distance. Answer Updated 6 days ago Show feedback bookmark_border1.0p3b Is the image real or virtual? Real Virtual Updated 6 days ago Show feedback bookmark_border1.0p3c Suppose the object is brought to a distance of 10.3 cm in front of the lens. Where is the image now with respect to its previous location? (Note: Ensure the sign convention you use is consistent by treating all image distances on the object side of the lens as negative.) Answer Updated 7 minutes ago Show feedback bookmark_border1.0p3d How has the height of the image changed if the object is 84.2 cm tall? Answerarrow_forwardn object is placed 37.4cm in front of a diverging lens with a focal length of 18.1 cm. Please provide your answers in units of cm if necessary. bookmark_border1.0p3a Find the image distance. Answer Updated 6 days ago Show feedback bookmark_border1.0p3b Is the image real or virtual? Real Virtual Updated 6 days ago Show feedback bookmark_border1.0p3c Suppose the object is brought to a distance of 10.3 cm in front of the lens. Where is the image now with respect to its previous location? (Note: Ensure the sign convention you use is consistent by treating all image distances on the object side of the lens as negative.) Answer Updated just now Show feedback bookmark_border1.0p3d How has the height of the image changed if the object is 84.2 cm tall? Answerarrow_forwardCan you draw a FBD and KD please!arrow_forward
- If a 120- volt circuit feeds four 40-watt fluorescent lamps, what current (in amps) is drawn if the power factor is 0.912 0.33 0.68 1.21 3.3arrow_forwardHow do you draw a diagram of the ruler and mass system in equilibrium identifying the anti-clockwise torque and clockwise torque? How do I calculate the anti-clockwise torque and the clockwise torque of the system with the ruler and the washers, does it come from the data in table 2? Please help, thank you!arrow_forwardA long, narrow steel rod of length 2.5000 m at 33.5°C is oscillating as a pendulum about a horizontal axis through one end. If the temperature drops to 0°C, what will be the fractional change in its period?arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningCollege PhysicsPhysicsISBN:9781938168000Author:Paul Peter Urone, Roger HinrichsPublisher:OpenStax CollegeCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningUniversity Physics Volume 1PhysicsISBN:9781938168277Author:William Moebs, Samuel J. Ling, Jeff SannyPublisher:OpenStax - Rice UniversityPhysics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning





