#(d v)/(d t)=a(t)#
#d v=a(t)*d t#
#int d v=int a(t) *d t#
#v=int(5t-10) *d t#
#v=5*t^2/2-10*t+C#
#t=0 rarr v=0 rarrc=0#
#v=5/2 t^2-10t#
#v_a=1/(5-3)int_3^5 |(5/2 t^2-10t)|d t#
#v_a=1/2[|5/2*t^3/3-10*t^2/2|_3^5]#
#v_a=1/2[(5/2*5^3/3-5*5^2)-(5/2*3^3/3-5*3^2)]#
#v_a=1/2[(625/6-125)-(45/2-45)]#
#v_a=1/2[(625-750)-(-45/2)]#
#v_a=1/2[-125+45/2]#
#v_a=|-51.25 |#
#v_a=51.25 m/s#