static forces problem

Question

Perry (5.20 kg) slides down a ramp (26° relative to horizontal).

Starting from rest, the platypus slides a diagonal distance of 2.1 m in 4.8 s.

What is the coefficient of kinetic friction between the platypus and the ramp?

Answer 1

Hi Kalani D.,

It's time to make some assumptions. Assume that the platypus path is at a 45 degree angle away from "directly downhill" on the ramp. Then the driving force on the platypus is gravity, at sin(26 degrees) / (2^0.5) , because the diagonal path doesn't have as much drop per unit run. That's ~0.310g (maximum, before kinetic friction retards)

That, plus d=(1/2)at^2 (for a = net acceleration) should get you to your goal.

By the way, let Perry do this -- the male platypus has venomous spurs on hind limbs. The venom has interesting properties -- including a peptide with a D-amino acid, the only such known in mammals.

-- Cheers, --Mr. d.