a 5-ton bus stopped on a ramp at a 30-degree angle. What is the friction force with the ground, in newtons, to keep it from sliding down the slope?

2500 N

Explanation:

Draw a free body diagram of the bus.  There are three forces:

Weight force mg pulling down,

Normal force N pushing perpendicular to the ramp,

and friction force F pushing parallel to the ramp.

Sum of forces in the parallel direction:

∑F = ma

F − mg sin θ = 0

F = mg sin θ

F = (5000 N) (sin 30°)

F = 2500 N

nah.   i'm just sleepy.

ice to water 1 water to vapour 2 latent heat