V(t)=20t^2-100t+50 when will the acceleration of the particle becomes zero

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.

b. a lightning bug, plug of grass, and a worm

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m