Two people pull on the wagon each with a constant 20N force. Both people pull to the left. What is the Net Force on the wagon?

Abeam has a square cross-section, a x a, where a is the linear dimension, and is subject to a pure bending moment, m. m is known with an uncertainty of 10% and a is known with an uncertainty of 5%. the strength of the material is known to an uncertainty of 12%. find the minimum design factor such that the beam is guaranteed not to fail.

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

Which is not true about oxygen-17 and oxygen-18?