Uh it's c) 0.5 :), and for some reason i need to write 20 characters to explain it well, okay you need to divide speed/wavelength, that's it
Answer: For number 9, the children would not be able to close the box.
Explanation: The combined force of the children is 55 N. The box spring overpowers them with 60 N. I hope this helps!
The amplitude of a wave corresponds to its maximum oscillation of the wave itself.
In our problem, the equation of the wave is
![y(x,t)= (0.750cm)cos(\pi [(0.400cm-1)x+(250s-1)t])](https://tex.z-dn.net/?f=y%28x%2Ct%29%3D%20%280.750cm%29cos%28%5Cpi%20%5B%280.400cm-1%29x%2B%28250s-1%29t%5D%29)
We can see that the maximum value of y(x,t) is reached when the cosine is equal to 1. When this condition occurs,

and therefore this value corresponds to the amplitude of the wave.