12. A plastic ruler is rubbed on a cotton shirt. The ruler gains a positive charge. Which of the following statements is true?
A. Protons jumped ON TO the ruler from the shirt.
B. Protons jumped OFF OF the ruler and on to the shirt.
C. Electrons jumped ON TO the ruler from the shirt.
D. Electrons jumped OFF OF the ruler and on to the shirt.

The image shows a pendulum in simple harmonic motion the pendulum starts at a and swing to e

This is important 1. what happens to the speed of molecules in water vapor when it condenses to form a liquid? (2 points) the molecules slow down. the molecules speed up. the molecules slow down and then speed up. the molecules speed up and then slow down. 2. how might human activities change to compensate for a decrease in water supplies? (2 points) humans might build a factory. humans might build drainage systems. humans might extract more water from the ground. human behavior does not change because of the water cycle. i'll be grateful if anyone can answer these 2 questions !

The atoms in a nickel crystal vibrate as harmonic oscillators with an angular frequency of 2.3 × 1013 rad/s. the mass of a nickel atom is 9.75 × 10-26 kg. what is the difference in energy between adjacent vibrational energy levels of nickel? (h = 6.626 × 10-34 j • s, , 1 ev = 1.60 × 10-19 j)