Which of these observations of galileo refuted ptolemy's epicycles? the craters on the moon the rotation of sunspots across the sun's surface the revolution of jupiter's moons around it the complete cycle of venus' phases the visibility of many more stars with the telescope?

An ideal spring has a spring constant (force constant) of 2500 n/m, is stretched 4.0 cm, how much elastic potential energy does it possess? (a) 3j (b) 0.00j (c) 1j (d) 2j (e) 4j

Chemical energy is a form of energy. a. heat b. kinetic c. potential d. electromagnetic

You have a resistor and a capacitor of unknown values. first, you charge the capacitor and discharge it through the resistor. by monitoring the capacitor voltage on an oscilloscope, you see that the voltage decays to half its initial value in 2.70 miss . you then use the resistor and capacitor to make a low-pass filter. what is the crossover frequency fc?