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Mechanics 1- Connected Particles

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A train consists of an engine of mass 50,000kg coupled to two trucks A and B of masses 10,000kg and 6,000kg. The train moves along the track horizontally at constant deceleration. The tension in the coupling between truck A and truck B is zero.

i) By applying newtons second law to truck B, show that the deceleration is 0.25ms^-2

ii) Find the tension in the coupling between the engine and A

iii) Determine whether the engine exerts a driving force or a braking force and find its magnitude.

No idea how to go about this, any ideas on a method to work this out, all questions on my assignment are simular to this one.
Reply 1
Avatar for 0range
0range
20
F=ma
the mass is 6000 and the force is -1500
rearrange to find the deceleration

Can't remember how to do ii or iii atm, I'll edit this if I remember
(edited 12 years ago)
If this is a university assignment, we can't really help you.

Mark T the tension in the towbar between the engine and A. It points both ways into the centre of the towbar.

Mark X the driving force at the front of the engine (remember it could be a braking force but it will just come out with a negative magnitude if this is the case).

Apply F = ma on whatever sections you like.
(edited 12 years ago)
Reply 3
Avatar for Luppy021
Luppy021
OP
6
Original post by Mr M
If this is a university assignment, we can't really help you.

Mark T the tension in the towbar between the engine and A. It points both ways into the centre of the twobar.

Mark X the driving force at the front of the engine (remember it could be a braking force but it will just come out with a negative magnitude if this is the case).

Apply F = ma on whatever sections you like.


Not a university assignment! It's M1 as level, okay I'll try your method be back in 10
Reply 4
Avatar for raheem94
raheem94
13
Original post by Mr M
If this is a university assignment, we can't really help you.

Mark T the tension in the towbar between the engine and A. It points both ways into the centre of the towbar.

Mark X the driving force at the front of the engine (remember it could be a braking force but it will just come out with a negative magnitude if this is the case).

Apply F = ma on whatever sections you like.


I get a positive tension and a negative X for this question.

I took X in the right direction, but due to the negative answer it is acting at left, so its a braking force. But why is the tension positive, shouldn't it be negative, because won't the braking force cause thrust?
(edited 12 years ago)
Original post by raheem94
I get a positive tension and a negative X for this question.

I took X in the right direction, but due to the negative answer it is acting at left, so its a braking force. But why is the tension positive, shouldn't it be negative, because won't the braking force cause thrust?


I think you can answer the question yourself by looking at the system as a whole or, if you have already done that, look at the forces on the engine. You will find the equations are not consistent.

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