Is friction more in rougher or slippery surface? And why would it be very difficult to walk on a polished platform? Help pls. Yu'll be marked brainlies :)))

How many dots must be added to the symbol to properly represent a standard nitrogen ion? a) 1 b) 3 c) 5 d) 8

Astone is dropped with no initial velocity from the top of a cliff and hits the ground a time of 3.9 s later. what is the height of the cliff, in units of meters? you may assume that air resistance is negligible. give the answer as a positive number question 15 a figure skater is rotating at a rate of 200 revolutions per minute. what is the angular speed, in units of rad/s? 200 o 20.9 12000 o 3.33

What is the weight of a feather (mass = 0.0001 kg) that floats through earth's and the moon's atmospheres?