Question

A pendulum consists of an object of mass m = 1 kg swinging on a massless string of length l = 258 cm. The object has a speed of 1.6 m/s when it passes through its lowest point. What is the greatest angle with the vertical that the string makes during the motion of the object?


So I tried doing this by calculating GPE = mgh
=-25.3
So does this mean KE = 25.3?
However I don't even use the velocity at the lowest point, I am extremely confused...help =S
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Answer 1

find the KE at the lowest point: 1/2 m v^2

Now, take that value,and set it equal to mgh
find h.
That is the height the bob goes up.

Now, angle= arccos(l-h)/l

make your drawing, and confirm that.

Answer 2

Yes I see what you're saying after drawing the diagram...So for the first bit we just use plain substitution of GPE formulas and second bit is trig.

=) thanks that seemed easier than i thought.