Solución

a.   v(t)=11+t2v\left( t \right) = {1 \over {1 + {t^2}}}

b.   $$$a\left( t \right) = {{ - 2t} \over {{{\left( {1 + {t^2}} \right)}^2}}}$$$

c.   (a) 0.20.2, 0.060.06, 0.030.03   (b) 0.16-0.16, 0.028-0.028, 0.0088-0.0088

d.   El disco de hockey está desacelerando a los 2, 4 y 6 segundos