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Help please: Mechanics connected particles

An engine of mass 60000 kg pulls a truck of mass 12000 kg along a horizontal track. The engine experiences a resistance to motion of 80N per kg and the truck a resistance of 50N per kg. Given that the train is travelling at a constant speed, find the tractive force of the engine and the tension in the coupling between engine and truck.

Since it's constant speed the resistance to motion should equal the forward motion right? But I'm stuck when it comes to finding the tension...

Posted from TSR Mobile
The tractive force of the engine is the force required to move both itself and the truck against friction.
The tension in the coupling is the force required to move just the truck.
Reply 2
Avatar for JK96
JK96
5
Original post by sefulK
An engine of mass 60000 kg pulls a truck of mass 12000 kg along a horizontal track. The engine experiences a resistance to motion of 80N per kg and the truck a resistance of 50N per kg. Given that the train is travelling at a constant speed, find the tractive force of the engine and the tension in the coupling between engine and truck.

Since it's constant speed the resistance to motion should equal the forward motion right? But I'm stuck when it comes to finding the tension...

Posted from TSR Mobile


The acceleration is 0. So ΣF=0. Resolve the horizontal forces on just the engine or the truck but not the whole system.
Reply 3
Avatar for sefulK
sefulK
OP
Since there's no acceleration is the tractive force equal to the sum of all the horizontal forces resistant to motion?
Original post by sefulK
Since there's no acceleration is the tractive force equal to the sum of all the horizontal forces resistant to motion?


Yes the forces are balanced. The tractive force = resistive force for no acceleration.
Reply 5
Avatar for sefulK
sefulK
OP
Thanks, and what about the tension? Resultant force = mass x acceleration.
Therefore considering the truck:
T - (50 x 12000) = 12000 x 0
Which gets me to T = 60000 but when I consider the engine the tension is something else and I'm sure the tension should be the same when considering either particle. Right?

Posted from TSR Mobile
I stated what the tension in the coupling is in post #2
The tension in the coupling is just the force required to pull the truck.
This is, as you state, 50 x 12,000 = 600,000N (Not 60,000N)

The total force produced by the engine is also what I stated in post #2
It's equal to the total resistive force on the two combined. This is the total force that has to be balanced.
So its 600,000N plus the resistive force on the engine.
Reply 7
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Millerman
7
are you doing M1?
Reply 8
Avatar for sefulK
sefulK
OP
Ok thanks, I get it now!
Reply 9
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sefulK
OP
Yeah

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