Physics - help please

Question

Michelle swings a 0.009-kg rubber stopper around her head. The rubber stopper is tied to a string that Michelle holds at 0.72 m while swinging it once every 0.5s. What is the minimum force she needs to apply to securely hold the string?

Answer 1

Hi Hannah

 

Here is the way to do it

Centripetal force = mv²/r

 

m= mass , v= speed and r = radius or length of string in this case

 

m= 0.009 kg

 

r = 0.72 m and  T = time for one full swing

 

v = rw =2 pi r/ T = 2*3.14 *0.72/0.5 = 9.04 m/s

Force = 0.009 * 9.04*9.04/ 0.72 = 1.02 N = Minimum force required to keep it going