college physics
posted by Thomas .
Each of four particles moves along an xaxis. Their coordinates (in meters) as functions of time (in seconds) are given by:
Particle #1: x(t)=2t^24
Particle #2: x(t)= 3t4
Particle #3: 2t^24
Particle #4: 2 *[sq. root (t+1)] 4
Which of these particles are speeding up for 0<t< infinity?
a)#1 only
b)#1,3,4
c)all four
d)none
e)#1,4

If you consider "speeding up" to be an increase in speed, regardless of direction, then none of the choices is correct.
#2 and #3 accelerate, backwards. The others start out by slowing down.
They may be referring to increasing speed as an increase in V in the positive direction.
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