問題詳情

4. A child plays a string of length = 20 cm connected with a ball of mass m = 1 kg, and starts to rotate it vertically. Find the minimum speed of the ball at the top that is needed to rotate it vertically in circular fashion? 

(Gravitational acceleration g = 10 m/s2 )
(A) 0.7 m/s
(B) 1.4 m/s
(C) 2.2 m/s
(D) 3.3 m/s
(E) 4.2 m/s

參考答案

答案：B

統計：A:0,B:1,C:0,D:0,E:0

難度：計算中