Force and Translational Dynamics unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
The coefficient of friction has no units
Newton's first law
Vertical circular motion
Tension
Why the normal force is not always mg
Why heavier objects do not fall faster
Free-body diagram errors
Connected objects
Force as the slope of momentum
Newton's third law
Banked curve
Centripetal force is not a new force
Short answer 1. Define or explain: Normal force on an incline
3 ptsShort answer 2. Define or explain: Inclined plane components
3 ptsShort answer 3. Define or explain: The ideal pulley assumption
3 ptsShort answer 4. Define or explain: Normal force
3 ptsFree response
10 ptsEXPERIMENTAL DESIGN AND ANALYSIS (Question 3, 10 points). Students investigate friction. A block of unknown mass is released near the top of a curved ramp; friction is negligible on the ramp but not on the horizontal surface the block slides onto (Figure 1). The students must vary a single quantity and collect data that can be graphed to determine the coefficient of kinetic friction μk between block and horizontal surface. They have access to only a meterstick. For parts C–D: in a different experiment, a block is released from rest a distance d up a rough ramp inclined at θ = 30°, sliding down through a photogate near the bottom that measures its speed v (Figure 2). Table 1: d = 0.20, 0.30, 0.40, 0.50, 0.60 m with v = 0.29, 0.38, 0.41, 0.49, 0.52 m/s. The students correctly determine v² = [2g(sinθ − μk·cosθ)]·d, and create a graph with d on the horizontal axis.
A(i). Indicate quantities the students could measure to determine μk using a linear graph. A(ii). Briefly describe a method to reduce experimental uncertainty for the measured quantities.
B(i). Indicate what quantities to graph on the horizontal and vertical axes to create a linear graph usable to determine μk, stating which quantity goes on each axis. B(ii). Briefly describe the relationship between μk and a feature of that graph (an equation may be included).
C(i). Label the vertical axis of Figure 3 with a measured or calculated quantity (with units) so the graph is linear and usable to determine μk. C(ii). Create the graph: numerical vertical scale, plotted points. C(iii). Draw a best-fit line.
D. Using the best-fit line from part C(iii), calculate an experimental value for μk.