Calculating Kinetic Energy for a Swinging Wrecking Ball

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To calculate the potential energy of a 315kg wrecking ball at a 30º angle from the vertical, one must determine the height it has been raised from its lowest position. The potential energy (PE) can be calculated using the formula PE = mgh, where 'm' is mass, 'g' is the acceleration due to gravity, and 'h' is the height. When the wrecking ball swings back to the vertical position, all potential energy converts to kinetic energy (KE), meaning KE = PE. The kinetic energy can then be calculated using the formula KE = ½ mv², allowing for the determination of the wrecking ball's speed as it returns to the vertical. Understanding the conservation of energy principle is key to solving this problem.
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A wrecking ball, with mass of 315kg, hangs from a crane on 10.0m of cable. If the crane swings the wrecking ball so that the angle that the cable makes with the vertical is 30.0º, what is the potential energy of the ball in relation to its lowest positio? What will be the kinetic energy of the wrecking ball when it falls back to the vertical position? What will be the speed of the wrecking ball?

I have no problem finiding the potential energy, but I don't know how to calculate the kinetic energy. and i know EK = ½ mv², but i don't know how to use it here. What should I do?
 
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In the system as you describe it, there is no loss of energy, so any potential energy is going to be converted completely into kinetic energy.
In other words, KE = PE!
 
Thanx alot
 
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