The density of iron is 7.87 g/cm3. If an iron cannonball has a volume of 105 cm3 what is the mass of the ball?

answer: i don't know the answer good luck

explanation:

what is the speed of a softball that travels 20m in 2secs

speed = 20/2 = 10 m/s

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