Posted by **Thomas** on Tuesday, August 24, 2010 at 3:30am.

Each of four particles moves along an x-axis. Their coordinates (in meters) as functions of time (in seconds) are given by:

Particle #1: x(t)=2t^2-4

Particle #2: x(t)= -3t-4

Particle #3: -2t^2-4

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

- college physics -
**drwls**, Tuesday, August 24, 2010 at 10:31am
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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