October 8, 2015

Homework Help: Physics

Posted by TechnoBoi11 on Thursday, February 1, 2007 at 3:05pm.

An electron's position is given by r = 4.00t i - 6.00t2 j + 5.00 k, with t in seconds and r in meters.

(a) In unit-vector notation, what is the electron's velocity v(t)? (Answer in terms of i, j, k, and t.)
___ m/s

(b) What is v in unit-vector notation at t = 8.00 s?
___ m/s

(c) What is the magnitude of v at t = 8.00 s?
___ m/s

(d) What angle does v make with the positive direction of the x axis at t = 8.00 s?
___ (from the +x axis)

..for (a), i got:


and for (b):


what am i doing wrong?

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