Two blocks are connected by a massless cord and are being pulled to the right by an external force F. They are accelerating at 2 m/s2. If needed, use g = 10 m/s2. With a coefficient of kinetic friction of 0.3, the external force acting on the 8 kg block is most nearly
A.55 N
B.26 N
C.40 N
D.65 N
E.39 N
ma =F –F(fr),
F = F(fr)+m•a =
=μ•m•g +m•a =
=m(μ•g +a)
=8(0.3•10+2) =40 N
ANSW: C.40 N