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AP Physics C: Mechanics 3.4 C Describe How the Selection of a System Determines Whether the Energy of That System Changes Questions

Describe how choosing a system boundary determines whether an interaction transfers energy across the boundary or transforms energy among stores within the system.

Syllabus
Effective Fall 2024
Course
AP Physics C: Mechanics

Exam points

  • choose a system boundary that classifies an interaction as internal transformation or external transfer
  • explain an apparent energy increase as work transferred into the selected system from outside
  • explain an apparent mechanical-energy decrease through dissipation or energy leaving the modelled system

AP Physics C: Mechanics 3.4 C Describe How the Selection of a System Determines Whether the Energy of That System Changes Questions question 1

[Maximum number: 3]

In Scenario 1, a system composed of two springs, A and B, and a block of mass m is at rest on a horizontal surface. Friction between the block and the surface is negligible. Each spring is attached to a fixed wall and the block, as shown in Figure 1. Spring A has a spring constant k and Spring B has a spring constant 2 k. Each spring is at its relaxed length when the block is at position x=0, as shown.

Figure 1

Figure 1

The block is moved to x=x1x=x_{1} and held at rest, as shown in Figure 2.

Figure 2

Figure 2

In Scenario 1, the block oscillates with period T. The position x of the block in Scenario 1 as a function of time t is shown in Figure 4.

Scenario 1

Scenario 1

In Scenario 2, the block-springs system is placed on a new surface. There is friction between the block and the new surface. The block is again moved to the same position x=x1x=x_{1} and released from rest. The block completes multiple oscillations with the same period as in Scenario 1 before coming to rest.

On the axes shown in Figure 5, sketch a graph of the kinetic energy K of the block as a function of t for Scenario 2.

Scenario 2

Scenario 2

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