Simple trig which I have forgotten

  • Thread starter NOP90
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In summary: Sorry mate, it's 0.33m, originally 330mm but I am working in SI units.(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.The ball is hanging at a height of (r sqrt(3)/2, -r/2).
  • #1
NOP90
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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 :blushing: and need help finding out the height.
 
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  • #2
NOP90 said:

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 :blushing: 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.
 
  • #3
Mark44 said:
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.
 
  • #4
Mark44 said:
(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 = ?
 
  • #5
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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1. What is the definition of trigonometry?

Trigonometry is a branch of mathematics that deals with the relationships between the sides and angles of triangles.

2. What are the three basic trigonometric functions?

The three basic trigonometric functions are sine (sin), cosine (cos), and tangent (tan).

3. How do you find the missing side of a right triangle using trigonometry?

You can use the Pythagorean theorem (a^2 + b^2 = c^2) to find the missing side of a right triangle. You can also use the trigonometric functions by setting up ratios between the known sides and the unknown side.

4. What is the unit circle and how is it used in trigonometry?

The unit circle is a circle with a radius of 1 unit. It is used in trigonometry to help solve for the values of trigonometric functions for any angle.

5. How do you convert degrees to radians and vice versa?

To convert degrees to radians, multiply the degree measure by pi/180. To convert radians to degrees, multiply the radian measure by 180/pi.

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