Okay, now I see the third scenario clearly. The yellow box indicates this surface has "a lot of friction." For Position 1, there is a bar chart with a high blue bar for Kinetic Energy (KE) and no bars for Potential Energy (PE) or Thermal Energy (E_thermal). For Position 2, there is a very small blue bar for KE, a small red bar for E_thermal, and no bar for PE.
This scenario follows the same logic as the second one but with more friction. As the wheel rolls from Position 1 to Position 2 on a flat surface, a significant portion of its initial kinetic energy is converted into thermal energy due to the high friction. The remaining kinetic energy at Position 2 is very low, which means most of the energy has been dissipated as heat. Again, the total energy should be conserved: the initial KE equals the final KE plus the E_thermal generated.
Now that I have analyzed all three scenarios, I can summarize the solution for each one.
Solution
The task is to complete the energy bar charts for a rolling wheel under different friction conditions. The key principle is the conservation of energy: the total energy (Kinetic Energy + Potential Energy + Thermal Energy) remains constant, although it can transform between these forms.
Here is the solution for each scenario:
Scenario 1: Frictionless Surface
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Condition: No friction means no energy is lost to heat.
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Analysis: The decrease in Kinetic Energy (KE) from Position 1 to Position 2 must be matched by an increase in Potential Energy (PE), indicating the wheel rolled up an incline.
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Solution: At Position 2, draw a bar for Potential Energy (PE) that is equal in height to the amount that the Kinetic Energy (KE) bar decreased. The Thermal Energy (E_thermal) bar should remain at zero.
Scenario 2: Some Friction
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Condition: Some friction is present, so some kinetic energy is converted to thermal energy.
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Analysis: The wheel is on a flat surface (no change in PE). The decrease in KE from Position 1 to Position 2 is exactly equal to the increase in E_thermal.
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Solution: At Position 2, the Thermal Energy (E_thermal) bar should be drawn to a height that represents the amount of KE lost. The Potential Energy (PE) bar should remain at zero.
Scenario 3: A Lot of Friction
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Condition: High friction causes a large amount of kinetic energy to be converted to thermal energy.
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Analysis: The wheel is on a flat surface (no change in PE). The large decrease in KE from Position 1 to Position 2 corresponds to a large increase in E_thermal.
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Solution: At Position 2, the Thermal Energy (E_thermal) bar should be drawn to a height that represents the large amount of KE lost. The Potential Energy (PE) bar should remain at zero. The remaining KE bar will be very small.
Parent Tip: Review the logic above to help your child master the concept of energy bar graphs worksheet answers.
