(e) What is acceleration at instant t = 40 s ? (20%)

題組內容

4. A palm tree sways back and forth with a period of 15 s, and Jack estimate the amplitude of the motion of the treetop to be 1.5 m. Jack begins timing at some instant after the treetop passes through the upright position, and after you have been watching this motion for 40 s, the treetop is 0.5 m to the left of the upright position of time.

2. A research vessel performs a river survey. The vessel moves downstream with a constant speed 6 m/s relative to the water. The river has a steady current of 1 m/s relative to the ground. Mary sits on the boat and his instrument falls into the river. Five minutes later, she notices that his instrument is missing and immediately turns the boat around, moves upriver with the same speed of 6 m/s relative to the water. How long does it take the man to row back upriver to reclaim his instrument ? (20%)

題組內容

(e) What is acceleration at instant t = 40 s ? (20%)

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