) At a certain instant, a particle-like object is acted on by a force Upper F Ov
ID: 1776062 • Letter: #
Question
) At a certain instant, a particle-like object is acted on by a force Upper F Overscript right-arrow EndScripts equals left-parenthesis 2.80 N right-parenthesis i Overscript EndScripts minus left-parenthesis 2.80 N right-parenthesis j Overscript EndScripts plus left-parenthesis 5.00 N right-parenthesis k Overscript EndScripts while the object's velocity is v Overscript right-arrow EndScripts equals negative left-parenthesis 1.40 m divided by s right-parenthesis i Overscript EndScripts plus left-parenthesis 4.50 m divided by s right-parenthesis k Overscript EndScripts. What is the instantaneous rate at which the force does work on the object? (b) At some other time, the velocity consists of only a y component. If the force is unchanged, and the instantaneous power is -11.0 W, what is the velocity of the object just then? (Give your answer without a unit vector.)
Explanation / Answer
a)
F= (2.80i – 2.80j+5.00k)N
v= (-1.40i+4.50k)m/s
W=F.v = (2.80i – 2.80j+5.00k).(-1.40i+4.50k)
W= (2.80*-1.40)+(5.00*4.50)
W = 18.58 J
b)
W=Fy.vy
-11.0 = -2.80*v
v= -11.0/-2.80
v = 3.93 m/s
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