What is the mechanical advantage of a ramp that makes an angle of 15 degrees?

On mars a rock falls an unknown vertical distance from a resting position and lands in a crater. if it takes the rock 2.5 seconds to fall, how high is the cliff the rock fell from? mars' surface gravity is 3.8 m/s2.

What describes the particles in a liquid

Why did thomson's results from experimenting with cathode rays cause a big change in specific thought about atoms ?