Beginning with the equation, ρR = ρsubstance /ρwater show that , Relative Density = mass of substance / mass of water
i. e ρR = msubstance /mwater , if the volume are equal
( you must prove that the equation is true)

Waves are used in many practical applications to support work, entertainment, and health. one example is the use of ultrasound imaging to safely track the development of a growing fetus. what is a specific example of a practical application of waves in medicine, entertainment, safety, or other fields? provide a brief explanation of how the properties of waves are useful to that application.

Alfred pushes on a heavy box, but cannot move it. the box has a lot of inertia motion friction gravity

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?