A 5.00 kg crate is on a 21.0° hill. Using X-Y axes tilted down the
plane, what is the x-component
of the normal force?
(Unit = N)

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?

Afisherman notices that his boat is moving up and down periodically without any horizontal motion, owing to waves on the surface of the water. it takes a time of 2.20 s for the boat to travel from its highest point to its lowest, a total distance of 0.670 m . the fisherman sees that the wave crests are spaced a horizontal distance of 5.80 m apart. (a) how much is the wavelength? (b) find the period of the wave. (c) how fast are the waves traveling? (d) what is the amplitude a of each wave?

Consider a hydrogen atom in the ground state. what is the energy of its electron? =e= jj now consider an excited‑state hydrogen atom. what is the energy of the electron in the =5n=5 level? =e5= j