Equilibrium Question Involving boat and scale

[Coolcatss]

Homework Statement

A trailer carrying a boat is supported by a scale which initially reads 48 kg. The boat (and therefore its centre of gravity) is moved 0.15 m further back on the trailer. The scale now reads 37 kg. Find the mass of the boat (Ignore the 6.0 m distance because it was not given and therefore is unknown.)
http://members.shaw.ca/barry-barclay/Self-Tests/test06/q15.gif

Homework Equations

ΣT=0[/B]
Initial Mass= 48 kg
Final Mass= 38 kg
unknown distance of the boat= x
Center of gravity distance= 0.15 m

The Attempt at a Solution

I didn't know where to start with the x distance of the boat (used to be 6.0 m) in which, is needed to solve for the mass of boat. If someone can help put me on the right track, that would be awesome. [/B]

 

[haruspex]

Initial Mass= 48 kg
Final Mass= 38 kg

No, those are not masses. They are readings on the scale. What weights correspond to those readings?
Draw a free body diagram of the trailer. What forces act on it and where? (Put in unknowns as necessary.)
What torque balance equation looks useful?

 

[Emcee Delta Tea]

I'm 8 years late here! Ha ha, great question, but without the length of the boat trailer, let's call it L, the mass of the boat would be 73.3 L. There is mention of 6 m in the original question? That's a long boat trailer, but if that's what it is, then the boat would be 440 kg.

 

[haruspex]

I'm 8 years late here! Ha ha, great question, but without the length of the boat trailer, let's call it L, the mass of the boat would be 73.3 L. There is mention of 6 m in the original question? That's a long boat trailer, but if that's what it is, then the boat would be 440 kg.

Unfortunately the diagram link no longer works. I agree with your answer, except that I would have thought it requires the boat to have been moved 0.15m closer to the tow bar, which I would have described as moving it forward, not back.

But I don't see how knowing the length of the trailer changes the answer.