Centripetal Forces Physics

Question

Imagine a 2 kg toy plane hanging from a string and moving in a horizontal circle of radius 2 m. The tension in the string is 50N. What is the speed of the plane? Start with a FBD and FNET = ma.

Answer 1

Since all the motion is horizontal, we can ignore gravity.  Assuming the string is also horizontal,

 

F = mv²/r

 

v = √(Fr/m) = √[(50 N)(2m) / (2 kg)] = 7.07 m/s

 

If the string is at some other angle, the analysis is more complicated.