A cargo plane unloads crates of supplies at the site of

Question

Problem: A cargo plane unloads crates of supplies at the site of humanitarian disaster. The crates slide down a 48 foot long ramp that starts at the cargo plane door 17 feet above the ground. If the ramp has a coefficient of kinetic friction of 0.12,

Part A: How long does it take each create to slide down the ramp?

I need help to find how long does it take each create to slide down the ramp.