Simple trig which I have forgotten

[NOP90]

Homework Statement

Small ball fastened to a piece of string 0.33m in length. The ball is displaced by 60 degrees from the vertical. What is the height of the ball at this point?

Homework Equations

sin? cos? tan?

The Attempt at a Solution

This is part of a bigger physics question in which I need to work out potential energy (mass*9.8*height). I have forgotten my basic trigonometry and need help finding out the height.

 

[Mark44]

Homework Statement

Small ball fastened to a piece of string 0.33m in length. The ball is displaced by 60 degrees from the vertical. What is the height of the ball at this point?

Homework Equations

sin? cos? tan?

The Attempt at a Solution

This is part of a bigger physics question in which I need to work out potential energy (mass*9.8*height). I have forgotten my basic trigonometry and need help finding out the height.

Is the string 1/3 m or .33m? If it's given as 1/3 m. don't use such a crude approximation as .33m. If it's given as .33 m, then you're OK.

An equivalent problem is this: Pull the ball to the right so that the string is horizontal. Swing the ball down by 30 degrees. If the string's length is r meters, and the string is fastened at the origin (0, 0), the position of the ball will be (r cos(-30 deg.), r sin(-30 deg.)) = (r sqrt(3)/2, -r/2). All you have to do is figure out how high this point is above the low point when the ball is hanging straight down.

 

[NOP90]

Is the string 1/3 m or .33m? If it's given as 1/3 m. don't use such a crude approximation as .33m. If it's given as .33 m, then you're OK.

Sorry mate, it's 0.33m, originally 330mm but I am working in SI units.

 

[NOP90]

(r cos(-30 deg.), r sin(-30 deg.)) = (r sqrt(3)/2, -r/2). All you have to do is figure out how high this point is above the low point when the ball is hanging straight down.

I'm a bit confused with that. So the length of string is 0.33m. Do I calculate 0.33*cos(-30deg.)? What does the comma between rcos(-30deg.) and rsin(-30deg) represent? Do I use both calculations? Do I also calculate what is on the right of the = ?

 

[Mark44]

Yes, r = .33. The comma between rcos(-30deg.) and rsin(-30deg) is there because these are the x and y coordinates of a point.

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