A physics student investigates static friction by attaching a spring scale to a block…
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
A physics student investigates static friction by attaching a spring scale to a block of mass 1.2kg on a rough ramp. The student slowly increases the ramp angle θ while keeping the spring scale oriented parallel to the ramp and pulling up the ramp just enough to prevent motion until the block is on the verge of sliding down. The scale readings T (in newtons) for various angles are shown in the table.
Angle θ (degrees): 10, 15, 20, 25, 30
Scale reading T (N): 0.88, 1.9, 3.0, 4.2, 5.5
Complete the tasks below.
(a) Using the data, construct a linear plot that will allow determination of the coefficient of static friction μs from the slope. Clearly state which quantities you choose for the horizontal and vertical axes, and explain why this choice should produce a straight line.
(b) Derive the theoretical relationship between your chosen plotting variables, starting from Newton’s laws applied to the block at incipient motion.
(c) Determine the experimental value of μs by calculating the slope of the best-fit straight line through the data points. Show sample calculations, including units.
(d) The accepted value for μs for these materials is 0.46. Calculate the percent error of the experimental value obtained in part (c) and discuss two plausible sources of systematic error in the procedure that could account for the discrepancy.