The figure shows a snapshot graph at t = 4 s of a wave traveling at 0.5 m/s to t

Question

The figure shows a snapshot graph at t = 4 s of a wave traveling at 0.5 m/s to the right.

(a) Redraw the snapshot graph but at t = 0 s so you are drawing D(x, t = 0).

(b) Draw the history graph, D(x = 3m, t), for the point at x = 3 m. Be sure to show your work, especially how you found the time when the leading edge of the wave passed through x = 3m.

(c) Now suppose that the wave were traveling at 2 m/s to the left instead but that its snapshot graph at t = 4 s was otherwise as shown in Figure 1(a). Draw the history graph, D(x = 3m, t) of the point at x = 3 m for this case.

Explanation / Answer

: ?x = vx t ? v x = ? x t = 24.0 m 3.03 s = 7.92 m s .27. The pilot of an airplane traveling 180 km/h wants to drop supplies to flood victims isolated on a patch of land 160 m below. The supplies should be dropped how many seconds before the plane is directly overhead? Choose downward to be the positive y direction. The origin is the point where the supplies are dropped. In the vertical direction, vy0 = 0, ay = 9.81 m/s2, y0 = 0, and the final position is y = 160 m. The time of flight is found from applying Eq. 2-11b to the vertical motion. y = y0 + v y 0 t + 1 a y t 2 2 ? 160 m = 0 + 0 + 1 2 ( 9.80 m s ) t 2 2 ? 2 (160 m ) t= = 5.71 s 9.80 m s 2 Note that the speed of the airplane does not enter into this calculation.47. A swimmer is capable of swimming 0.45 m/s in still water. (a) If she aims her body directly across a 75-m- wide river whose current is 0.40 m/s how far downstream (from a point opposite her starting point) will she land? (b) How long will it take her to reach the other side? r Answer: Call the direction of the flow of the river the x direction, and the v water rel. shore direction straight across the river the y direction. Call the location of the swimmer

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