Asled of mass 80 kg starts from rest and slides down an 18° incline 90 m long. it then travels for 20 m horizontally before starting back up a 16° incline. it travels 90 m along this incline before coming to rest. what is the net work done (in j) on the sled by friction?

net work done by friction = - 2205 J

Explanation:

given,

mass of sled = 80 kg

slide down at an angle of 18°

length = 90 m

travel horizontally = 20 m before  starting back up a 16° incline.

net work = ?

net work done by friction = change in potential energy

                                          = mg (h_f - h_i)

                                          = (75) (9.8) (- 27.81 + 24.81)  

net work done by friction = - 2205 J

waves moving from a fast medium to a slow medium will experience a reflection as light travels more slowly than red light. total internal reflection occurs when the critical angle is.

true tan speed = ang vel x radius