not sure where to post this, resolving forces

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red and white kop!

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a boat on a trailer is held in equilibrium on a slipway inclined at 20° to the horizontal, by a cable inclined (upward) at theta° to a line of greatest slope of the slipway. The combined mass of the boat and trailer is 1250kg. The cable may break if the tension exceeds 7000N. Find the max value of theta.

this looked fairly straightforward to me so i used 12500cos60 = 7000cos(theta) at max tension to get theta<26.8°, but this is wrong!
i cant find where...
 
red and white kop! said:
a boat on a trailer is held in equilibrium on a slipway inclined at 20° to the horizontal, by a cable inclined (upward) at theta° to a line of greatest slope of the slipway. The combined mass of the boat and trailer is 1250kg. The cable may break if the tension exceeds 7000N. Find the max value of theta.

this looked fairly straightforward to me so i used 12500cos60 = 7000cos(theta) at max tension to get theta<26.8°, but this is wrong!
i cant find where...
Click to expand...

From where did you get 60?
 
red and white kop! said:
good point
is everything correct otherwise?
Click to expand...

Yes - so your equation would be:

T * cos(@) = 1250 * g * cos(70°) - It seems you assumed g = 10 m/s[sup:2maotusu]2[/sup:2maotusu] instead of 9.81m/s[sup:2maotusu]2[/sup:2maotusu]
 
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