Find tension in this train coupling

[Doubell]

1. Homework Statement [/b

A railway engine of mass 100 tonnes is attahched to a line of trucks of total mass 80 tonnes. assuming there is no resistance to motion find the tension in the coupling between the engine and the leading truck (a) when the train has an acceleration of 0.020 ms/1^2
,(b) is moving at constant velocity. ( 1 tonne = 1.0 x 10^3 kg.)

Homework Equations

F= m*a

The Attempt at a Solution

for part (a) the tension in the coupling would be equal to the force acting on the train since the coupling is a device merely tranfering the force acting on the train to pull the trucks it is linked to. using force = mass * accelleration we can calculate the force of the train to be 80 000 kg *0.02 ms/s^2 which = 1.6 * 10^3 N. for part (b) the force acting on the couple would be 0 N since the velocity is constant there can be no acceleration because accelleration is the rate of change of velocity this implies that the force = 0 N since the acceleration = 0 m/s^2. mass * acceleration = force = 0 N are these answers right

 

[zorro]

Yes they are right ( except for the units of Tension ).