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butterflydreamer
 one year ago
check my answer please :) SIMPLE HARMONIC MOTION 
Question: The rise and fall of the ride at the mouth of a river is assumed to be simple harmonic motion. The depth of water at low tide is 0.7m and the depth at high tide is 3.7m.
If low tide occurred at 8:55am and high tide at 3:05pm, find the earliest time at which the boat could enter the mouth of the river if it required the water to be at least 2m deep.
My solution:
http://prntscr.com/7d1ex1
butterflydreamer
 one year ago
check my answer please :) SIMPLE HARMONIC MOTION  Question: The rise and fall of the ride at the mouth of a river is assumed to be simple harmonic motion. The depth of water at low tide is 0.7m and the depth at high tide is 3.7m. If low tide occurred at 8:55am and high tide at 3:05pm, find the earliest time at which the boat could enter the mouth of the river if it required the water to be at least 2m deep. My solution: http://prntscr.com/7d1ex1

This Question is Closed

butterflydreamer
 one year ago
Best ResponseYou've already chosen the best response.1Low tide at 8:55am is 0.7m High tide at 3:05 pm is 3.7m Therefore, centre at 12:00pm will be 2.2m Amplitude = 1.5 Period = 2pi/n = ?

IrishBoy123
 one year ago
Best ResponseYou've already chosen the best response.2i suggest you calculate the period as you have the amplitude the period, T, is time for a complete oscillation. you go from trough to peak during times 8:55am to 3:05 pm. isn't that half an oscillation? once you have T, you can then use \( \omega = \frac{2 \pi}{T}\) in your shm equation: \(y  y_0 = A cos( \omega t + \phi)\), if that is how you are presenting it.

butterflydreamer
 one year ago
Best ResponseYou've already chosen the best response.1ohhh okayyy! Give me a minute or so to work it out :)

butterflydreamer
 one year ago
Best ResponseYou've already chosen the best response.1wait.. if 8:55am  3:05 pm is HALF an oscillation.. that is 6hrs and 10 minutes... So it takes 12 hrs and 20 minutes for a complete oscillation.. Therefore w = 740 (12hrs10 mins) Sooo... 2pi/n = 740 n = pi/370 dw:1433425233117:dw dw:1433425384627:dw

IrishBoy123
 one year ago
Best ResponseYou've already chosen the best response.2dw:1433425997658:dw

butterflydreamer
 one year ago
Best ResponseYou've already chosen the best response.1oops i wrote that wrong LOL. Every part which says 360 should be 370 :)

IrishBoy123
 one year ago
Best ResponseYou've already chosen the best response.2dw:1433426031745:dw yes, but method looks good haven't checked your calcs or answer

IrishBoy123
 one year ago
Best ResponseYou've already chosen the best response.2dw:1433426180829:dw

butterflydreamer
 one year ago
Best ResponseYou've already chosen the best response.1soz? LOL Oh dear.. i made so many errors _ OKAY i will write it out on paper because that's the easiest method.

IrishBoy123
 one year ago
Best ResponseYou've already chosen the best response.2final: i assume adding \(\pi \) on RHS somehow negates the fact it is a negative cosine. only saying because i would need to work it through to get it, and don't have time  but I suspect it is a little trick that you use regularly....

butterflydreamer
 one year ago
Best ResponseYou've already chosen the best response.1yeah, it is a trick that i found online LOL. Okay basically if i write my working out properly, it will look like this: http://prntscr.com/7d1ex1

butterflydreamer
 one year ago
Best ResponseYou've already chosen the best response.1alrighties thank you so muccch! :)
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