RADAR (Radio Detection and Ranging) uses microwaves, a type of radio wave but usually specific microwave band. Often answer is microwaves. But radio waves also correct. I'll specify microwave as typical answer. Could be radio. Better: microwave. Many exams say microwaves. I'll stick with B.
Explanation:
Resistance depends on the resistivity of the material (R = ρL/A). Silver and copper are excellent conductors with very low resistivity. Aluminum is also a good conductor. Nichrome is an alloy (nickel, chromium, and often iron) with a resistivity about 60 times higher than that of copper, making it a resistor used in heating elements.
Explanation:
Potential energy: gravitational (mgh), elastic (½kx²). Kinetic energy due to motion. Total mechanical energy sum conserved in conservative forces.
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