A short train consists of two locomotives, each of mass 20 tonnes, with a truck of mass
10 tonnes coupled between them, as shown
in Figure 20.51. The resistances to forward
motion are 0.5 kN on the truck and 1 kN
on each of the locomotives. The train is
travelling along a straight, horizontal section
of track
Figure 20.51
a
Initially there is a driving force of 15 kN from
the front locomotive only.
(0)
Calculate the acceleration of the train.
Draw a diagram indicating the horizontal
forces acting on each part of the train,
including the forces in each of the
couplings. Calculate the forces acting on
the truck due to each coupling.
On another occasion each of the locomotives
produce a driving force of 7.5 kN in the same
direction and the resistances remain as before.
lii) Find the acceleration of the train and
the forces now acting on the truck due
to each of the couplings. Compare your
answer to this part with your answer to
part (ii) and comment briefly. [MEI