Qes el conocimiento y su definición

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.

There are multiple tuning forks present in the room, and annie strikes one with a natural frequency of 400 hz. which of these other tuning forks will begin to vibrate through resonance and make the sound louder? a 200 hz tuning fork a 400 hz tuning fork a 800 hz tuning fork a 1600 hz tuning fork

An airplane is flying with a velocity of 240 m/s at an angle of 30.0∘ with the horizontal, as the drawing shows. when the altitude of the plane is 2.4km,a flare is released from the plane. the flare hits the target on the ground. what is the angle θ?