1. ## Force

A tractor of mass 1000 kg tows a trailer of mass 1000kg . The total resistance is 4000 N and is constant . One quarter of the total resistance acts on the trailer . Initially the acceleration of both the tractor and trailer is 2.0 m/s^2 . Finally , both of them move with the same uniform speed of 6.0 m/s . What is the force on the tractor along the tow-bar when

(a) acceleration is 2.0 m/s^2

(b) the tractor and trailer move at 6.0 m/s

I need some explaination here . THanks .

2. Originally Posted by thereddevils
A tractor of mass 1000 kg tows a trailer of mass 1000kg . The total resistance is 4000 N and is constant . One quarter of the total resistance acts on the trailer . Initially the acceleration of both the tractor and trailer is 2.0 m/s^2 . Finally , both of them move with the same uniform speed of 6.0 m/s . What is the force on the tractor along the tow-bar when

(a) acceleration is 2.0 m/s^2

(b) the tractor and trailer move at 6.0 m/s

I need some explaination here . THanks .
The horizontal forces acting on the trailer are the friction force (1000 N) and the tension force T from the tow bar. Hence Fnet = T - 1000.

But Fnet = ma = (1000)(a). Therefore:

(a) T - 1000 = (1000)(2).

(b) T - 1000 = (1000)(0). Note that a = 0 since velocity is constant.

3. Originally Posted by mr fantastic
The horizontal forces acting on the trailer are the friction force (1000 N) and the tension force T from the tow bar. Hence Fnet = T - 1000.

But Fnet = ma = (1000)(a). Therefore:

(a) T - 1000 = (1000)(2).

(b) T - 1000 = (1000)(0). Note that a = 0 since velocity is constant.

THanks Mr fantastic . But i am a bit confused . The question asks for the force acting on the tractor . But the working in (a) seems to be the force acting on the trailer .

Or perhaps they are equal ? THanks for explaining .

4. Originally Posted by thereddevils
THanks Mr fantastic . But i am a bit confused . The question asks for the force acting on the tractor . But the working in (a) seems to be the force acting on the trailer .

Or perhaps they are equal ? THanks for explaining .
The forces are equal in magnitude and opposite in direction (see Newtons Third law).