A 1000 kg engine pulls a train of 4 wagons each of 2500 kg along a horizontal railway track. If the engine exerts a force of 50000 N on wagons and track offers force of friction 10000 N, then calculate
(i) The net accelerating force
(ii) The acceleration of the train
(iii) The force of wagon-1 on wagon-2

Explanation

Force exerted by the engine is ` F_(1) = 50,000 N`
Frictional force exerted by the track , `F_(2) = -10000 N `
Negative sign shows that friction is opposite to the direction of motion .
(i) Therefore, net accelerating force ` vec (F)= vec (F_(1)) = vec (F_(2))`
`= 50, 000 + (- 10,000) `
` = 40 , 000 N`
(ii) Mass of each wagon of the train = 2500 kg
Number of wagons of the train = 4
` :. "Mass of the train (m)" = 2500 xx 4
` = 10,000 kg
Net accelerating force acting on the train is
` F= 40,000 N`
From ,
F = ma
` a = F/m`
` = (40,000)/(10,000) `
` = 4 m//s^(2)`
(iii) Mass of one wagon `(m_(1)) = 2500 kg `
Acceleration of the train ` a = 4 m//s^(2)`
Force exerted by wagon -1 on wagon -2 is the accelerating force for the three rear wagons.

` F' = 3 xx 2500 xx 4 m//s^(2)`
` = 30,000 N`