Elsa runs 100m. She takes 20s to run this distance. What is Elsa's average speed?

Explain earth's motion, using the terms "precession" and "rotation" in your answer.

It is really hard for me right know

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 3.00 ms . you then use the resistor and capacitor to make a low-pass filter. what is the crossover frequency fc?