Two flywheels of negligible mass and different radii are bonded together and rotate about a common axis (see below). the smaller flywheel of radius 13 cm has a cord that has a pulling force of 50 n on it. what pulling force (in n) needs to be applied to the cord connecting the larger flywheel of radius 22 cm such that the combination does not rotate?

Explanation:

As we know that the combination is maintained at rest position

So we will take net torque on the system to be ZERO

so we know that

here we will have

so we have

so we have

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