A block of mass rests on a horizontal rough surface
PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
A block of mass 3.0kg rests on a horizontal rough surface. A horizontal pulling force Fapp is slowly increased from 0N to 20N, then slowly decreased back to 0N. The coefficients of friction between the block and the surface are μs=0.45 and μk=0.30. Assume the surface is perfectly level and air resistance is negligible.
(1) Part 1: (a) On axes whose horizontal axis represents the applied force magnitude Fapp and whose vertical axis represents the magnitude of the friction force on the block, sketch the qualitative graph for the entire cycle of increasing and then decreasing Fapp. Clearly label numerical values for all breakpoints on both axes.
(2) Part 2: (b) Identify the interval of your graph during which the block remains at rest. Explain, in words, how the behavior of the friction force in that interval prevents the block from sliding.
(3) Part 3: (c) Describe how and why the graph changes once the applied force exceeds the largest value you found in part (b). In your explanation, discuss the physical meaning of any sudden change in the plotted curve.
(4) Part 4: (d) After the block has been sliding for several seconds, the applied force is slowly reduced. Referencing your graph, describe the subsequent motion of the block and the corresponding path the plotted point follows back toward the origin.