can someone pls explain how to solve these questions

7. A paddle in a ripple tank is observed to oscillate with a frequency of 20.0 Hz. If the water wave produced has a speed of 0.400 m s'1 . what is the period of the waves? Assume one rise and fall of the paddle corresponds to one wave. (a) 8 ms (b) 50 ms (c) 100 ms ((1) 400 ms Continued overleaf 50 8. Following from the previous question, what is the wavelength of the waves? (a) 0.02 m (b) 0.2 m (c) 2 m (d) 20 m 9. A cog wheel has 72 evenly spaced teeth and is turning at a constant speed of 105 revolutions per minute while a thin strip of metal is held against the cogs. What is the frequency of vibration of the metal strip? (a) 41 Hz (b) 105 Hz (c) 126 Hz ((1) 7560 Hz The following three questions relate to the information here: Ripples radiate out from vibrating source in water. After 6.00 s. 42 ripples have been generated with the rst ripple covering a distance of 3.00 m from the source (each ripple constitutes a wave). 10. What is the wavelength of the ripples? (a) 0.048 m (b) 0.071m (c) 0.43 m (d) 3.0 m 1 1. What is the frequency of the ripples? (a) 14 Hz (b) 7.0 Hz (c) 0.33 Hz (d) 0.17 Hz 12. What is the speed of the ripples? (a) 0.1 m s'1 (b) 0.2 m 5'1 (c) 0.4 m s'1 (d) 0.5 m s'jl