Answers:
a) 10 m
b) time=1.6 s, frquency=0.625 Hz
c) 6.25 m/s
Explanation:
a) If there is a crest at each dock and another three crests between the two docks, and the wavelength
is the distance between to crests; this means we have
in
:

Clearing
:


b) This part can be solved by a Rule of Three:
If 10 waves ---- 16 s
1 wave ----- 
Then:

This is the period of the wave
On the other hand, the frequency
of the wave has an inverse relation with its period
:


This is the frequency of the wave
c) The speed
of a wave is given by the following equation:


Finally:

Answer:
Explanation:
We shall take the help of vector form of displacement . Taking east as i and north as j
4.0m N = 4 j
7.5 m E = 7.5 i
6.8 m S = - 6.8 j
3.7 m E, = 3.7 i
3.6 m S = - 3.6 j
5.3 m W = - 5.3 i
3.7 m N, = 3.7 j
5.6 m W = - 5.6 i
4.4 m S = - 4.4 j
4.9 m W = - 4.9 i
Total displacement = 4j +7.5 i -6.8j+3.7i-3.6j-5.3i+3.7j-5.6i-4.4j-4.9i
= -4.6 i -7.1 j
magnitude of displacement = 
= 8.46 m
Direction
Tanθ = 7.1/ 4.6
θ = 57⁰ south of west .
distance walked = 4+7.5 +6.8+3.7+3.6+5.3+3.7+5.6+4.4+4.9
= 49.5 m