Erwin schrödinger developed the quantum model of the atom. what scientific knowledge was necessary for schrödinger’s work?
a. the discovery of the electron
b. the discovery of gamma rays
c. the invention of computers for complex calculations
d. the invention of microscopes for seeing subatomic particles

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg