Una partícula se mueve sobre el eje x de acuerdo con la ecuación del movimiento s=f(t) donde s es la distancia dirigida al origen en pies a los t segundos.
a) La velocidad v(t) y la aceleración a(t) en el instante t.
b) El instante t en el que la velocidad es cero.
s= 6t-t²
s=t²-6t
s= t²-9t+24

a)

s= 6t-t² -->  v = 6 -2t  --> a = -2

s=t²-6t  --> v = 2t-6       -->    a = 2

s= t²-9t+24  -->  v = 2t -9   -->  a = 2

b)

v = 6 -2t  = 0  --> t = 3

v = 2t-6  = 0   --> t = 3

v = 2t -9   = 0 --> t = 9/2

Step-by-step explanation:

si s(t) es la distancia, la velocidad es la primera derivada v(t) = s'(t)

y la acceleracion es la segunda derivada : a(t)= v'(t) = s''(t)

s= 6t-t² -->  v = 6 -2t  --> a = -2

s=t²-6t  --> v = 2t-6       -->    a = 2

s= t²-9t+24  -->  v = 2t -9   -->  a = 2

- "runner b is moving at a slower rate."

- "the graphs shown are graphs of distance(km) against time(min).

the slopes of this graphs are are given by:

slope = (change in y)/(change in x)

= (change in distance)/(change in time)

this is the formula for finding the speed. so, the slope of these graphs represent the speed of the runner.

taking each division in the graph to represent 1 on both axis:

runner a ⇒ speed = (2-0)/(1-0)

= 2/1

= 2 km/min

runner b ⇒ speed = (3-0)/(3-0)

= 3/3

= 1 km/min

this shows that   runner b is moving at a slower rate."