PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
Two identical blocks, X and Y, each of mass m, rest in contact on a horizontal surface that can be considered frictionless. A constant horizontal force of magnitude F is exerted on block X toward block Y so that the two–block system accelerates to the right.
Answer the following questions about the interaction between the blocks as they accelerate together.
(a) Draw a clearly labeled free-body diagram for block X and a separate free-body diagram for block Y.
(b) Compare the magnitudes and directions of all forces acting on block X with the corresponding forces acting on block Y. Support your comparison with reasoning based on physical principles.
(c) Discuss whether the contact force that block X exerts on block Y is an internal or external force when the two blocks are treated as a single system. Explain why this distinction is important for applying Newton’s second law to the system as a whole.
(d) Suppose instead that the blocks have unequal masses, with mX=2m and mY=m. Without doing any calculations, predict qualitatively how the contact force between the blocks would change, and justify your prediction.