Mcat pendulum question~~

[johnwandering]

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A pendulum consists of an object of mass m = 1.65 kg swinging on a massless string of length l. The object has a speed of 1.97 m/s when it passes through its lowest point. If the speed of the object is 0.87 m/s when the string is at 70° below the horizontal, what is the length of the string?

The relavent info is
Ek= 1/2 mv^2
Ep= mgh

 

[bajoneswadup]

A pendulum consists of an object of mass m = 1.65 kg swinging on a massless string of length l. The object has a speed of 1.97 m/s when it passes through its lowest point. If the speed of the object is 0.87 m/s when the string is at 70° below the horizontal, what is the length of the string?

The relavent info is
Ek= 1/2 mv^2
Ep= mgh

I'm just guessing, but wouldn't you find energy change and
divide that by the ac, since ac = tension? could be wrong

 

[dmf2682]

A pendulum consists of an object of mass m = 1.65 kg swinging on a massless string of length l. The object has a speed of 1.97 m/s when it passes through its lowest point. If the speed of the object is 0.87 m/s when the string is at 70° below the horizontal, what is the length of the string?

The relavent info is
Ek= 1/2 mv^2
Ep= mgh

I get roughly 1.6 m without using a calculator. What are the choices?