Whаt is slоwing the cаrt? (20 pоints) Students test а cart cоnnected by a light string over a pulley to a hanging mass. The cart moves right along a level track as the hanging mass moves down. They release the system from rest and use a motion sensor to record cart velocity. Acceleration is found from the slope of each velocity–time graph. Their first calculation assumes the track is frictionless and the string and pulley are ideal. They also run a control trial: disconnect the string and hanging mass, push the 1.00 kg cart to the right, and record how it slows down on the same track with the same motion sensor. The other cart mass used in the main trials is 1.50 kg . Use g = 9.80 m/s² . Take right for the cart and down for the hanging mass as positive. Main trials Trial Cart mass (kg) Hanging mass (kg) Acceleration from velocity–time slope (m/s²) A 1.00 0.200 1.14 B 1.00 0.300 1.81 C 1.00 0.400 2.38 D 1.50 0.200 0.63 E 1.50 0.400 1.60 Selected sensor readings Time since start (s) Trial A velocity (m/s) Coast-down velocity (m/s) 0.00 0.00 1.20 0.50 0.57 0.90 1.00 1.14 0.60 1.50 1.71 0.30 Show your work. Draw free-body diagrams for the connected cart and hanging mass. Include a possible force the students left out of their model. Also draw a force diagram for the cart while it coasts alone. (3 pts) Use the raw velocity readings to calculate the acceleration for Trial A and for the coast-down test. Explain the signs. (2 pts) Starting with Newton’s second law for each mass, develop the frictionless acceleration equation. Use it for Trials A and D and compare both predictions with the recorded values. (3 pts) From the coast-down test, estimate the resistive force on the lighter cart and a value for the kinetic friction coefficient. What must you assume to use that coefficient for the heavier cart? (3 pts) Now include friction in the connected-system equation. Recalculate A and D and compare your results with the table. (3 pts) What do you think the students overlooked? Support your explanation with three numerical observations, at least one from the coast-down test. Give one other possible cause the data cannot completely exclude. (4 pts) Describe one follow-up test that would help separate your explanation from the alternative. State what you would change, what you would keep the same, and what result you would expect. (2 pts) Upload ONE PDF at the end of the exam containing all of your written solutions. Do not upload a separate file for this question.
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Which оne оf the fоllowing is NOT а sub-period of Ancient Greece?