An 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a
horizontal track. If the engine exerts a force of 40000N , calculate the acceleration of the train.
To find the acceleration of the train , I divided 40000N by mass of 5 wagons.
But in the book the mass of the engine was also included for finding the acceleration.
I cannot understand how is the force of 40000 N acting on (engine + wagons). According to me this should only act on the wagons as the engine is applying this force.
Best Answer
The question is ambiguous, but I think we are meant to assume that the engine exerts a force of $40000$ N on the track. From the reaction force of $40000$ N on the engine some part, say $F_1$, is acting to accelerate the engine itself and some other part, say $F_2$, is exerted on the wagons. The acceleration of the engine and of the wagons is the same, so if this acceleration is $a$ then
$F_1 = 8000a \\ F_2 = 10000a \\ 40000 = F_1 + F_2 = 18000a \\ \Rightarrow a = \frac{40000}{18000}$