The graph displays the temperature over time for an unknown substance. Which of the following correctly identifies segment XY and why?

A.
Melting, because the substance has a freezing/melting point of 290°C.

B.
Melting, because energy is being added, but the temperature is not changing

C.
Vaporization, because the substance cannot be heated beyond a temperature of 290°C.

D.
Vaporization, because energy is being added, but the temperature is not changing.

Acave rescue team lifts an injured spelunker directly upward and out of a sinkhole by means of a motor-driven cable. the lift is performed in three stages, each requiring a vertical distance of 10.0 m: (a) the initially stationary spelunker is accelerated to a speed of 4.90 m/s; (b) he is then lifted at the constant speed of 4.90 m/s; (c) finally he is decelerated to zero speed. how much work is done on the 68.0 kg rescue by the force lifting him during each stage?

Which is the best predictor of the radioactive nature of an isotope? o the proton-to-electron ratio the neutron-to-proton ratio o the neutron-to-electron ratio the electron-to-proton ratio

Which atomic model was proposed as a result of j. j. thomson’s work?