Question

60.0 kg boy and a 40.0 kg girl are sitting in identical office chairs in a large warehouse. The coefficients of static and kinetic friction between the chairs and the horizontal floor are both 0.250. The boy puts his feet up against the girl’s chair and pushes it with a constant force of 375 N for 0.600 s. Determine how far apart the children come to rest.
4.

Answer 1

The objects are moving due to the law of the conservation of linear momentum
0 = m1•v1 + m2•v2,
F•Δt = m1•v1,
v1 = F•Δt/ m1 =375•0.6/60 =3.75 m/s
F•Δt = m2•v2,
v2 = F•Δt/m2= 375•0.6/40 =5.625 m/s

m1•(v1)^2/2 = k•m1•g•s1
s1 =3.75^2/1•0.25•9,8 = 2.87 m
m2•(v2)^2/2 = k•m2•g•s2
s2 =5.625^2/1•0.25•9,8 = 1.61 m