AP Physics C: Mechanics 4.2 A Describe the Impulse Delivered to an Object or System Questions

Describe impulse as the vector time integral of net force, and calculate it from constant or variable force functions, force-time graph areas, and measured interactions.

Syllabus
Effective Fall 2024
Course
AP Physics C: Mechanics

Exam points

  • calculate impulse from a constant net force and the duration of its action
  • integrate a time-dependent force function to determine signed vector impulse
  • interpret signed area under a force-time graph as the impulse delivered
  • determine average force or interaction time from a known impulse and force profile
  • sum impulses from multiple forces or intervals to obtain the net impulse on a system

AP Physics C: Mechanics 4.2 A Describe the Impulse Delivered to an Object or System Questions question 1

[Maximum number: 5]

Two blocks, 1 and 2, slide toward each other on a horizontal surface. Block 1 has mass m and slides in the +x-direction with constant speed 2v02 v_{0}. Block 2 has mass 6 m and slides in the -x-direction with constant speed v0v_{0}, as shown in Figure 1. The blocks then collide and stick together. The collision occurs from time t=0 to t=tct=t_{c}. After the collision, where t>tct>t_{c}, the blocks move together with the same constant speed.

Figure 1

Figure 1

The diagrams in Figure 2 can be used to represent the momentum of blocks 1 and 2 before and after the collision. The momentum vector diagram for Block 1 before the collision is shown.

During the time interval 0ttc0 \leq t \leq t_{c}, a force F is exerted on Block 2 by Block 1 along the x-direction as a function of t that is modeled by F(t)=Fmaxsin(At)F(t)=F_{\max } \sin (A t), where A is a positive constant and Fmax F_{\text {max }} is the magnitude of the maximum force exerted on Block 2 by Block 1 during the collision.

Derive an expression for Fmax F_{\text {max }}. Express your answer in terms of m,v0,A,tcm, v_{0}, A, t_{c}, and physical constants, as appropriate. Begin your derivation by writing a fundamental physics principle or an equation from the reference information.

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