[单选题]
A small ball of mass m is attached to a
5 :g f)zuin /xdpn229u6czgzm string and moves in a vertical circu
j;mxo;n7; 7p iq(rpnje*n 1ppnin + 9qlar
1n;emnj;xnnp97p q*j; q oir i+(n7pppath of radius r
What is the minimum velocity v at the lowest point of the path for the ball to continue moving in a circular path at top of the circle?
A. 2mgr
B. $\frac{2mgr}{2}$
C. $\sqrt{2gr}$
D. $\sqrt{5gr}$
参考答案:
D
本题详细解析:
To calculate the minimum value of velocity at the lowest point, we need to calculate the minimum kinetic energy.
At the lowest point, the total energy is only kinetic energy and the potential energy is zero.
From the law of conservation of energy,
Total energy at the top = Total energy at the lowest point
At the top the minimum speed for a circular path to be maintained occurs when the centripetal force = weight of the ball
