During physical activity of high intensity, your heart will beat at a percentage of its maximum rate. which range shows the correct percentages
during this type of activity?
a. 40%-50%
b. 50%-70%
c. 70%-85%
d. 85%-100%

If you go to a nutrition store and buy a supplement, you can count on the fact that it is pure and safe because supplements are regulated, controlled, and inspected by the fda.

Glass is transparent to visibile light under normal conditions; however, at extremely high intensities, glass will absorb most of the light incident upon it. this works through a process known as multiphoton absorption. in this process, several photons are absorbed at the same time. if very intense light whose photons carry 2ev of energy is shined onto a material with a band gap of 4ev, that light can be absorbed through two-photon absorption, because two photons have the right amount of energy to bridge the band gap. what is the minimum number of photons of 800-nm light that are needed to equal or exceed the band gap of fused silica glass

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.