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ubbaken

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**An object in simple harmonic motion oscillates with a period of 4.00 s and an amplitude of 9.08 cm. How long does the object take to move from x=0.00 cm to x=5.07 cm?**

I set up my eqn like this: 0.0908cos(ωt)=0.0507

cos(ωt)=0.583

ωt=56.1

then with ω=90deg I get 0.623s which is slightly higher than I think the answer would be, and is ultimately incorrect.

I've tried working the problem out a number of times, in rad and degs to make sure I'm not making an error there, and I get the same answer.

**The velocity of an object in simple harmonic motion is given by v(t)= -(0.250 m/s)sin(17.0t + 1.00π), where t is in seconds. What is the first time after t=0.00 s at which the velocity is -0.120 m/s?**

for this one it seems like I just have to work it through to find t. When I do so, I get down to 17.0t+1.00π=28.7 (from using sin^-1=-.120/-.250) and then there is no answer that fits (0<t<5 approx.). Plus, in trying the answers, they are wrong.

also, I have another problem I posted about https://www.physicsforums.com/showthread.php?t=142893"

I'm pretty spent on these, any and all help would be appreciated.

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