Two small spheres with mass m = 14.8 g are hung by silk threads of length L = 1.23 m from a common point. When the spheres are given equal charges, so that q1=q2=q, each thread hangs at an angle θ = 30.0o from the vertical. The system is in equilibrium. Calculate the magnitude of q

In an old-fashioned amusement park ride, passengers stand inside a 3.0-m-tall, 5.0-m-diameter hollow steel cylinder with their backs against the wall. the cylinder begins to rotate about a vertical axis. then the floor on which the passengers are standing suddenly drops away! if all goes well, the passengers will “stick” to the wall and not slide. clothing has a static coefficient of friction against steel in the range 0.60 to 1.0 and a kinetic coefficient in the range 0.40 to 0.70. part a what is the minimum rotational frequency, in rpm, for which the ride is safe? express your answer using two significant figures. f f = rpm