B) A man is cutting down a tree with an axe. He hears the echo of the impact of the axe hitting the tree after 1.8 s.
i. What sort of obstacle could have caused the echo? [1]
ii. The speed of sound is 330 m/s. How far is the tree from the obstacle? [3]
c) Distinguish between the nature of sound waves in b and the water wave in a.

What are the north and south poles of a solenoid change with?

Ajoint produces movement when its angle decreases. which type of movement is it?

Acommon technique in analysis of scientific data is normalization. the purpose of normalizing data is to eliminate irrelevant constants that can obscure the salient features of the data. the goal of this experiment is to test the hypothesis that the flux of light decreases as the square of the distance from the source. in this case, the absolute value of the voltage measured by the photometer is irrelevant; only the relative value conveys useful information. suppose that in part 2.2.2 of the experiment, students obtain a signal value of 162 mv at a distance of 4 cm and a value of 86 mv at a distance of 5.7 cm. normalize the students' data to the value obtained at 4 cm. (divide the signal value by 162.) then calculate the theoretically expected (normalized) value at 5.7 cm.