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1.9.31 Formulate first order differential equations (A-level only)

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Question 42

An autonomous underwater vehicle (AUV) is released from the surface of the ocean and descends vertically towards the seabed.

a.

Using a simple model of constant acceleration 0.25 m s-2, a researcher predicts that the velocity of the AUV exactly 80 seconds after being released from rest is 20 m s-1. Show how the researcher has obtained this prediction.

[1]
b.

Using a refined model that accounts for fluid resistance, it is assumed that the AUV's acceleration, a m s−2a \text{ m s}^{-2}a m s−2, at time t t\,t seconds after release is given by

a=0.25−0.01v a = 0.25 - 0.01v a=0.25−0.01v

where v m s−1v \text{ m s}^{-1}v m s−1 is the velocity of the AUV at time ttt. Find an expression for v v\,v in terms of ttt.

[6]
c.

Compare the behavior of v v\,v as t→∞ t \to \infty\,t→∞ for both models.

[2]

1.9.31 Formulate first order differential equations (A-level only) Questions

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