What is the new rotation time of the merry-go-round?

  • Thread starter quickclick330
  • Start date
In summary, the playground merry-go-round has a moment of inertia of 50 kg m2 and a diameter of 2.2 meters. It initially completes one rotation in 0.5 seconds. When a 5.0 kg block is placed 1.0 m from the center, it takes 0.71 seconds to complete one rotation. The angular momentum remains the same since there is no external torque, and the final moment of inertia is calculated by adding the moment of inertia of the disk and the mass.
  • #1
quickclick330
83
0
[SOLVED] Not sure where to start...

10. A playground merry-go-round is mounted on a frictionless axle, so it can only rotate
in the horizontal plane. This object has a moment of inertia about the axle of I=50 kg m2,
and it has a diameter of 2.2 meters. Initially it is turning at a constant rate so that it
completes one revolution in 0.5 seconds. Standing next to it, you carefully place a block
of mass m= 5.0 kg on the rotating table, so that it sits a distance r=1.0 m from the center.
How long does it take to complete one rotation now?
1. 0.5 s
2. 0.55 s
3. 0.59 s
4. 0.63 s
5. 0.67 s
6. 0.71 s

all i have is that i found wi = 12.57 rad/s...but i don't know what to do after that?
 
Physics news on Phys.org
  • #2
Can you think of any quantity which will remain conserved?
 
  • #3
The moment of inertia?
 
  • #4
No, because the mass distribution has changed after you put the mass on it.

If there's no external torque on a body, then the angular momentum remains the same. So, you should find the initial and final angular momenta.
 
  • #5
so initial and final angular momentum should equal since there is no external torque on the system right?
 
  • #6
You said it.
 
  • #7
Thanks!
 
  • #8
I do have one more question...how do u recalculate the new moment of inertia?
 
  • #9
MI of the mass = mass*(dist from axis)^2
Final MI = MI of disk + MI of the mass
 
  • #10
okay, thanks
 

What are some tips for getting started on a scientific project?

1. Start by identifying your research question or hypothesis. This will guide your entire project and help you stay focused.

2. Conduct a thorough literature review to see what research has already been done on your topic and to gather background information.

3. Develop a detailed research plan outlining your methods, materials, and data analysis techniques.

4. Gather and organize all necessary materials and equipment before starting your experiment or study.

5. Don't be afraid to ask for help or advice from colleagues or mentors. Collaboration and feedback can greatly improve your project.

What are some common mistakes to avoid when starting a scientific project?

1. Not clearly defining your research question or hypothesis.

2. Skipping the literature review and not knowing what research has already been done on your topic.

3. Not developing a detailed research plan, leading to disorganized or incomplete data.

4. Not properly documenting and labeling data, making it difficult to analyze and interpret.

5. Rushing through the project and not allowing enough time for thorough research and analysis.

How can I stay organized and on track while starting a scientific project?

1. Use a calendar or timeline to set deadlines and keep track of tasks.

2. Keep detailed notes and records of your research and methods.

3. Use a designated space or lab notebook for your project to keep all materials and data organized.

4. Regularly check in with your research plan and make adjustments as needed.

5. Seek feedback and collaborate with others to stay motivated and on track.

What resources are available to help me get started on a scientific project?

1. Your school or university may have resources such as research labs, equipment, and mentors available to students.

2. Online databases and journals can provide access to previous research on your topic.

3. Professional organizations and conferences often offer resources and networking opportunities for scientists.

4. Consider reaching out to experts or colleagues in your field for advice or collaboration.

5. Your local library may have books or other resources on scientific research methods and techniques.

How can I ensure the validity and reliability of my scientific project?

1. Use appropriate and validated research methods and techniques.

2. Conduct thorough and unbiased data analysis.

3. Use control groups and proper experimental design to minimize confounding variables.

4. Verify your results through replication or peer review.

5. Be transparent and document all steps of your research for others to review and replicate.

Similar threads

Magnitude of Acceleration on Merry-Go-Round
    • Introductory Physics Homework Help
Replies
2
Views
1K
How Does Angular Momentum Remain Conserved in a Merry-Go-Round System?
    • Introductory Physics Homework Help
Replies
8
Views
2K
Conservation of Angular Momentum -- Child jumping onto a Merry-Go-Round
    • Introductory Physics Homework Help
Replies
18
Views
4K
Earth's rotation slows down slightly over time -- How much energy is lost?
    • Introductory Physics Homework Help
Replies
15
Views
1K
Physics merry-go-round problem
    • Introductory Physics Homework Help
Replies
27
Views
5K
Playground/merrygo round problem. Rotational kinematics
    • Introductory Physics Homework Help
Replies
5
Views
2K
What's the source of increase in rotational energy of carousel?
    • Introductory Physics Homework Help
Replies
9
Views
1K
Rotational Momentum: Calculating Angular Speed After Cockroach Stops
    • Introductory Physics Homework Help
Replies
2
Views
1K
The Rotational Inertia of a Merry Go Round
    • Introductory Physics Homework Help
Replies
1
Views
3K
Rotating rod of negligible mass attached to two point masses
    • Introductory Physics Homework Help
Replies
19
Views
3K

Hot Threads

Recent Insights

Back
Top