Sylvia stood a ringing alarm clock on top of a block of foam inside a bell jar when the air was removed from the bell jar with a vacuum pump the ringing sound stopped explain why removing the air made the ringing sound stop

Why should seat belts not be mandatory quick plz

Choose all the answers that apply. our solar system: is in a spiral galaxy no longer includes pluto is made mostly of empty space is in the andromeda galaxy is the only known system that supports life

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.