Rotational Inertia - Questions

The Rotational Inertia Concept Builder is comprised of 24 questions. The questions are divided into 12 different question groups. Questions in the same group are rather similar to one another. The Concept Builder is coded to select at random a question from each group until a student is successful with that group of questions.

The questions and question groups are organized into three different activities. The activities are differentiated as follows:

• Location, Location, Location  Question Groups 1-6: Students are provided two diagrams of two systems with equal mass but different distribution of mass relative to the axis of rotation. They must identify the system with the greatest rotational inertia.
• A Change of Axis  Question Groups 7-9: Students are provided two diagrams of two identical systems with equal mass but a different axis of rotation. They must identify the system with the greatest rotational inertia relative to the given axis of rotation.
•  Contraption Analysis  Question Groups 10-12: Students are provided two diagrams of a complex multipart system. Each system has the same parts but those parts are arranged differently. They must identify the system with the greatest rotational inertia.

The questions from each group are shown below. Teachers are encouraged to view the questions in order to judge which activity is most appropriate for their classes. We recommend doing all three activities. 

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Activity 1: Location, Location, Location
Question Group 1
Questions 1
Two identical solid disks are arranged along a solid bar at different locations. For which arrangement – A or B – is the rotational inertia (I) about the vertical axis the greatest?
   
 
Questions 2
Two identical solid disks are arranged along a solid bar at different locations. For which arrangement – A or B – is the rotational inertia (I) about the vertical axis the greatest?
   


 
Question Group 2
Questions 3
A ring (A) and a solid disk (B) have the same mass. That mass is concentrated along the rim of the ring and distributed uniformly about the disk. For which object – A or B – is the rotational inertia (I) about the axis the greatest?
 

 
Questions 4
A solid disk (A) and a ring (B) have the same mass. That mass is distributed uniformly about the disk and concentrated along the rim of the ring. For which object – A or B – is the rotational inertia (I) about the axis the greatest?
   

 
Question Group 3
Questions 5
Six identical solid disks are arranged along a solid bar at different locations. For which arrangement – A or B – is the rotational inertia (I) about the vertical axis the greatest?
 
Questions 6
Six identical solid disks are arranged along a solid bar at different locations. For which arrangement – A or B – is the rotational inertia (I) about the vertical axis the greatest?  

 
Question Group 4
Questions 7
A hammer is balanced on a finger with two different arrangements. For which arrangement – A or B – is the rotational inertia (I) about the axis the greatest?  
 
Questions 8
A hammer is balanced on a finger with two different arrangements. For which arrangement – A or B – is the rotational inertia (I) about the axis the greatest?
   

 

Question Group 5
Questions 9
Two different pendula are made using identical masses and strings of different lengths. For which pendulum – A or B – is the rotational inertia (I) about the axis the greatest?
 
Questions 10
Two different pendula are made using identical masses and strings of different lengths. For which pendulum – A or B – is the rotational inertia (I) about the axis the greatest?
 

Question Group 6
Questions 11
A tightrope walker is experimenting with two different balancing poles. The two poles have the same mass but pole A is longer than pole B. For which pole – A or B – is the rotational inertia (I) the greatest? The axis of rotation is the tightrope.
 
 
 
Questions 12
A tightrope walker is experimenting with two different balancing poles. The two poles have the same mass but pole A is shorter than pole B. For which pole – A or B – is the rotational inertia (I) the greatest? The axis of rotation is the tightrope.
   
 
 

 
Activity 2: A Change of Axis
Question Group 7
Questions 13
Consider the same door being rotated about two different axes – one aligned with its center (A) and one aligned with its edge (B). For which case – A or B – is the rotational inertia (I) the greatest?
 
Questions 14
Consider the same door being rotated about two different axes – one aligned with its edge (A) and one aligned with its center (B). For which case – A or B – is the rotational inertia (I) the greatest?
   

 
Question Group 8
Questions 15
A baseball bat is being rotated about two different axes – one located near the knob of the bat (A) and one located several inches up from the knob of the bat (B). For which case – A or B – is the rotational inertia (I) the greatest?
 
Questions 16
A baseball bat is being rotated about two different axes – one located several inches up from the knob of the bat (A) and one located near the knob of the bat (B). For which case – A or B – is the rotational inertia (I) the greatest?
   

 
Question Group 9
Questions 17
A 1-kg mass is secured to the end of a 1-meter stick. The meter stick is then rotated about two different axes – one located on the opposite end of the meter stick (A) and one located at its exact center (B). For which case – A or B – is the rotational inertia (I) the greatest?
 
Questions 18
A 1-kg mass is secured to the end of a 1-meter stick. The meter stick is then rotated about two different axes – one located at its exact center (A) and one located on the opposite end of the meter stick (B). For which case – A or B – is the rotational inertia (I) the greatest?  

 
Activity 3: Contraption Analysis
Question Group 10
Questions 19
Each contraption below consist of three identical, connected parts. The configuration of the parts is different. For which contraption – A or B – is the rotational inertia (I) about the vertical axis the greatest?
 

 
Questions 20
Each contraption below consist of three identical, connected parts. The configuration of the parts is different. For which contraption – A or B – is the rotational inertia (I) about the vertical axis the greatest?
   
 

 
Question Group 11
Questions 21
Each contraption below consist of three identical, connected parts. The configuration of the parts is different. For which contraption – A or B – is the rotational inertia (I) about the axis the greatest?
 
Questions 22
Each contraption below consist of three identical, connected parts. The configuration of the parts is different. For which contraption – A or B – is the rotational inertia (I) about the axis the greatest?  

 
Question Group 12
Questions 23
Each contraption below consist of seven identical, connected parts. The configuration of the parts is different. For which contraption – A or B – is the rotational inertia (I) about the axis the greatest?

 
Questions 24
Each contraption below consist of seven identical, connected parts. The configuration of the parts is different. For which contraption – A or B – is the rotational inertia (I) about the axis the greatest?