Two friends are carrying a crate of mass 200 kg up a flight of stairs. The crate has length 1.25 m and height 0.500 m, and its center of gravity is at its center. The stairs make a 45? angle with respect to the floor. The crate also is carried at an angle 45?, so that its bottom side is parallel to the slope of the stairs. The force each person applies is vertical. A) What is the magnitude of the upper person's force?B) What is the magnitude of the force applied by the bottom person?C) Is it best to be the person above or below on the stairs?

Wavelength,frequency,and energy are related.what happens to a wave as it’s wavelength gets shorter?

Clothing made of several thin layers of fabric with trapped air in between, often called ski clothing, is commonly used in cold climates because it is light, fashionable, and a very effective thermal insulator. so it is no surprise that such clothing has largely replaced thickand heavy old-fashioned coats. (a) consider a jacket made of five layers of 0.1-mm-thick synthetic fabric (k = 0.13 w/m·°c) with 1.5-mm-thick air space (k = 0.026 w/m·°c) between the layers. assuming the inner surface temperature of the jacket to be 28°c and the surface area to be 1.25 m2, determine the rate of heat loss through the jacket when the temperature of the outdoors is 0°c and the heat transfer coefficient at the outer surface is 25 w/m2·°c. (b) what would your response be if the jacket is made of a single layer of 0.5-mm-thick synthetic fabric? what should be the thickness of a wool fabric (k = 0.035 w/m·°c) if the person is to achieve the same level of thermal comfort wearing a thick wool coat instead of a five-layer ski jacket?

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?