# Homework Help: Locomotive forces problem

1. Jun 19, 2012

### foxat

A 2.1 kg toy locomotive is pulling a 1.7 kg caboose. The frictional force of the track on the caboose is 0.51 N backward along the track. If the train is accelerating forward at 3.4 m/s2, what is the magnitude of the force exerted by the locomotive on the caboose?

2. Jun 19, 2012

### SammyS

Staff Emeritus
Hello foxat. Welcome to PF !

What have you tried?

Where are you stuck?

You must show an attempt, before we can help you. --- those are the rules here at PF.

3. Jun 19, 2012

### foxat

Thanks!

I have approached this problem by using total F = ma, which equals the force exerted by the locomotive on the caboose minus the frictional force. So ma = F of the locomotive - 0.51, and thus F of the locomotive = ma + 0.51. The answer i came up with is (2.1 + 1.7)(3.4) + 0.51, or 13.43 N. Am I approaching this the right way?

4. Jun 20, 2012

### SammyS

Staff Emeritus
No.

What net force is needed to accelerate the caboose at 3.4 m/s2 ?

Also, do you know about Free Body diagrams ?