A child sits on the ground next to a remote-controlled toy car. At time t = 0, the car begins to move in a straight line directly away from the child. The variation with time t of the velocity of the car along this line is shown in [Figure 4.1]. The car's horn continually emits sound of frequency 925 Hz between time t = 0 and time t = 6.0 s. The speed of the sound in the air is 338 m s⁻¹.

1. (a)(i)Describe qualitatively the variation, if any, in the frequency of the sound heard, by the child, that was emitted from the car horn: (i) from time t = 0 to time t = 2.0 s[1]
2. (a)(ii)(ii) from time t = 4.0 s to time t = 6.0 s.[1]
3. (b)Determine the frequency, to three significant figures, of the sound heard, by the child, that was emitted from the car horn at time t = 3.0 s. frequency = ...................................................... Hz[2]
4. (c)Determine the time taken for the sound emitted at time t = 4.0 s to travel to the child. time taken = ...................................................... s[2]

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