How can an element be identified using its emission spectrum? a. by measuring the frequencies of the spectral lines, and calculating the energies that these correspond to b. by measuring the wavelengths of the spectral lines, and then calculating the differences between adjacent wavelengths c. by heating the unknown element, and then comparing the emitted spectrum with known spectra of the elements d. by identifying the color of the first line of the spectrum, and comparing this to a chart of known spectra

In a system, when potential energy decreases, then entropy also decreases. true false

Thomas his older brothers, who own a junk yard, on the weekends to earn extra money. he likes to them push broken-down cars to the back of the junk yard because it makes him feel strong. last saturday, they pushed three cars with different weights, and he noticed he used different amounts of force for each one. the cars were the following weights: white car: 2,700 kg red car: 1,500 kg blue car: 2,100 kg think about how much force is needed to move each car. which correctly lists the cars in order from the most to least amount of force needed to move them? a) white, blue, red b) blue, red, white c) red, white, blue d) white, red, blue

The uniform slender bar rests on a smooth horizon- tal surface when a force f is applied normal to the bar at point a. point a is observed to have an initial acceleration aa of 20 m/s2, and the bar has a corre- sponding angular acceleration of 18 rad /s2. deter- mine the distance b.