What is the Net Force Acting on a Truck and Trailer System?

[VeryJerri]

Homework Statement

A 1200 kg pickup truck tows a small 300 kg trailer using a relatively lightweight tow rope. The position of the trailer is given in m and time in s. *There is an animation which shows the truck pulling the trailer across X-axis.
Given: x= -20; y= +1 **BTW, i don't know what the given has to do with anything here! :x
Starts from zero ends at 16 seconds.

Homework Equations

I know F= ma. They did not give acceleration so I looked up my notes and found that:
if I set p=truck and r= trailer g=ground, then

a = Fpg - Frg/ (mp + mr) ... a= F/m

The Attempt at a Solution

but I'm not sure if I set that up right! I mean i took mass of truck (p) = 1200kg x 9.8 m/s^2 to give me 11760 N then mass of trailer (r) = 300 kg x 9.8 m/s^2 to give me 2940 N. (11760-2940/(1200+300) = 8820/1500 = a = 5.88.
So if F= ma, then F = 1500 x 5.88 which gives me 8820 N.

Is this correct? What should I do? Please help...physics scares me lol

OK, so i know its incorrect bc I got it wrong on my online homework (webassign). So...?

 

[PhanthomJay]

You are going to have to clarify the problem. Does the truck-trailer system travel 20 meters in 16 seconds? You'd have to calculate the acceleration, then the net force providng that acceleration. Welcome to PF.