21) The distance between crest and the adjacent trough of water wave is 3m They

1.67m

5m/s

Explanation:

Given parameters:

Wavelength of the wave = 3m

Speed of the wave  = 5m/s

Unknown:

Frequency of the wave  = ?

Speed of the water waves  = ?

Solution:

The distance between crest and the adjacent trough of water waves is known as the wavelength of a wave.

  To find the frequency ;

         V = f∧

V is the speed of the wave

f is the frequency

∧ is the wavelength

   Insert the parameters and find the frequency;

         f  = V/ ∧   = 5 / 3  = 1.67Hz

The rate at which the wave passed a given point is the speed of the wave and it is 5m/s

40 N/m

Explanation:

F = -kx (This is the Hooke's Law equation)

F is the force the spring exerts = 8 N

-k = spring constant

x = displacement (The distance stretched past it's natural length) = 20cm

x needs to be in meters, and 20 cm is = to 0.2 meters

Finally:

8N = -k (0.2m)

-k = 8N / 0.2 m

k = -40 N/m