What is force? what is the difference between contact and non-contact?

Which expression allows you to determine the mechanical advantage of an inclined plane? a. height of plane / input force b. length of plane / input force c. length of plane / height of plane d. height of plane / length of plane

The energy of a photon was found to be 3.38 × 10–19 j. planck’s constant is 6.63 × 10–34 j • s. which color of light corresponds to this photon?

What is the weight of a feather (mass = 0.0001 kg) that floats through earth's and the moon's atmospheres?