Question

i know how to do it, i keep getting the wrong answer!!

a bob of mass 4.00 kg is suspended from a fixed point by a massless string of length 1.50 m. The bob moves in a horizontal circle with the string always making an angle theta=22 from the vertical. what is the speed of the bob?

(tension is 42.3 N)

Answer 1

Look at the tension:
tension=mg/sinTheta
Now, the horizontal component of tension is tension*costheta, or mg/tantheta

That must equal centripetal force,
mv*2/radius.
the radius must be 1.50*sinTheta

so finally,
mv^2/1.5*sintheta =mg/tantheta
solve for v
check my thinking.

Answer 2

thank you so much!! it was so frustrating to get the wrong answer after wrong answer..