Rotational motion, energy conservation problem

AI Thread Summary
A uniform rod of mass 2 kg and length 2 m, pivoted at one end with a 1 kg mass at its tip, starts from a 30-degree angle and falls under gravity. The user attempts to calculate the speed of the tip when the rod is horizontal using energy conservation principles, specifically mgh = 1/2mv^2. They find a speed of 4.42 m/s but note that the expected answer is 4.8 m/s. The discussion also seeks clarification on writing the rotational kinetic energy of the system and calculating the total change in gravitational potential energy as it falls. The urgency of the problem is emphasized due to an impending test.
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rotational motion, energy conservation problem URGENT please help

Homework Statement



A uniform rod of mass M=2 kg and length L = 2m is pivoted from its end. It has a point mass m=1 kg on its tip. It stars from rest at an angle of 30 degrees above horizontal. It falls under the influence of gravity. How fast is the tip m moving when the rod is horizontal at θ
= 0

Homework Equations



mgh = 1/2mv^2

The Attempt at a Solution



h= Lsinθ = 1
m cancels from both sides
so you're left with
v=√2g=4.42

BUT, the actual answer given is 4.8

Help please! I have a test in just a few hours and have been trying to figure this problem out for awhile! Thanks
 
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How would you write the rotational KE of the system? Also, what's the total change in gravitational PE as it falls?
 

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