# Homework Help: Tractive force for wheeled vehicle

1. Feb 16, 2013

### siludavid

1. The problem statement, all variables and given/known data
a locomotive of mass 20 tonnes hauls a train of mass 200 tonnes up an incline of 1 in 200. the resistive force for the locomotive and the train is 40 newtons per tonne. the train accelerates from rest to 60km/h in 2km.determine;
a) the tractive force of the locomotive
b) the drawbar pull between the locomotive and the train

2. Relevant equations
F=R+mgsinθ+ma from the Newton's second law of motion

3. The attempt at a solution
part a
mass=20000kg
sinθ=0.005
R=800
s=2000m
u=0
v=16.67m/s2
a=0.069m/s2
by substituting the equation above F will be 3161N or 3.161KN
now in the second part is where am getting difficulty in solving how can it be approached please

Last edited: Feb 16, 2013
2. Feb 16, 2013

### tiny-tim

welcome to pf!

hi siludavid! welcome to pf!

the tractive force is found by using Ftotal = ma on the locomotive plus the train

the drawbar force is found by using Ftotal = ma on the train only

3. Feb 16, 2013

### siludavid

where will the angle of inclination and the resistive force be used in that case

4. Feb 16, 2013

### tiny-tim

uhh?

same in both cases …

your F = ma equation (in both cases) is parallel to the slope

(if you're not sure, write out the equations to show us)

5. Feb 16, 2013

### siludavid

according to me the tractive force minus the resistive force minus the resistive force due inclination which is mgsigθ because it always act on the opposite direction which will equal to ma that is;
F-R-mgsinθ=ma
therefore;
F=R+mgsinθ+ma
where R will be the resistive force together with mgsinθ

6. Feb 16, 2013

### tiny-tim

yes

(same formula for both questions)

7. Feb 16, 2013

### siludavid

now my problem is the drawbar remember it connects the train and the locomotive, will you find the tractive force in both locomotive and the train then find the difference between the two to get the pull or what should you do to get the drawbar pull

8. Feb 16, 2013

### tiny-tim

consider only the forces on the train …

you know what the acceleration is, and you know all the forces except the drawbar force