18. A particle starts from rest at r0=9.0(adsbygoogle = window.adsbygoogle || []).push({}); j(unit vector) m and moves in the xy-plane with the velocity shown in the figure below. the particle passes through a wire hoop located at r1=20im, then continues onward.

a. At what time does the particle pass through the hoop?

b. What is the value of v4y, the y-component of the particle's velocity at t=4s?

c. Calculate and plot the particle's trajectory from t=0 to t=4s

I know how to do part c, but can't do it without parts a and b. So far all I've done is sketch out the graphs on my paper as well as the graphs of their derivatives. Thefigure referenced in the problem is the following:

https://www.physicsforums.com/attachment.php?attachmentid=7841&stc=1&d=1159234661

graphs.JPG

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# Homework Help: Another Two-dimensional Dynamics Problem

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