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I R GOOD

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## Homework Statement

2.15

A turtle crawls a straight line, which we call the x-axis with positive direction to the right.Equation for the turtle's position as a function of time

is x(t)=50,0cm + (2,0cm/s)t - (0,625cm/s^2)t^2a.) find the turtle's initial velocity, initial position, initial acceleration

b.) at what time t is the velocity of the turtle zero (derivation?)

c.) how long after does it take the turtle to return to it's starting point

d.)At what time t is the turtle a distance of 10,0cm from it's starting poin

## The Attempt at a Solution

a.) Initial position at x(0)

50cm +(2cm/s)(0) -(0,065cm/s)(0)

=50cm

Initial velocity

x'(0) =0 + (2cm/s)(1) -(0,065cm/s^2)(2*0)

=2cm/s

initial acceleration

x''(0) = 0 + (-0,065cm/s^2)(2)

= -0,125cm/s^2

b.)

at what time t is the velocity of the turtle zero

x'(t)= 0 + (2cm/s)(1) - (0,065cm/s^2)(2t)

then x'(t) = 0

2cm/s - (0,0625cm/s^2)(2t) = 0

1cm/s =(0,0625cm/s^2)(t)

1cm/s / -0,0625cm/s^2=t

= -16sc.) how long after does it take the turtle to return to it's starting point

I tried

(-0,065cm/s^2)(t^2) + (2cm/s)(t) + 50cm = 0

QUADRATIC FORMULA

got either -16,49... or 48,3...

but answer should be 32ssame with d.)

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