How does frequency and pitch affect sound

What is the electric force acting between two charges of -0.0045 c and -0.0025 c that are 0.0060 m apart? use fe=kq1q2/r^2 and k = 9.00 x 10^9 n*m^2/c^2 a. 1.7 x 10^7 n b. -1.7 x 10^7 n c. -2.8 x 10^9 n d. 2.8 x 10^9 n

Rohit is trying to tune an instrument

The voltage applied across a given parallel-plate capacitor is doubled. how is the energy stored in the capacitor affected?