An incline, 2 masses, and a pulley. What could be more fun?

An incline, 2 masses, and a pulley. What could be more fun? (20:28)

A 55 g mass is attached to a light string, which is placed over a frictionless, massless pulley, and attached to a 199 g block which is on a board inclined at 39.3° as shown. Assuming the block starts at rest and the μk between the incline and block is 0.38, how long will it take the block to move 13 cm?
This is an AP Physics C: Mechanics topic.

Content Times:
0:00 The problem
1:18 Drawing the free body diagrams
6:23 Newton’s Second Law
12:44 Fixing our mistake
14:51 Finding the change in time
16:50 Demonstrating the answer
18:16 Finding the friction force direction
19:15 Reviewing the new things

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