Aclassroom that normally contains 40 people is to be airconditioned with window air-conditioning units of 5-kw cooling capacity. a person at rest may be assumed to dissipate heat at a rate of about 360 kj/h. there are 10 lightbulbs in the room, each with a rating of 100 w. the rate of heat transfer to the classroom through the walls and the windows is estimated to be 15,000 kj/h. if the room air is to be maintained at a constant temperature of 21°c, determine the number of window air-conditioning units required.

Two polarizers are oriented at 70∘∘ to one another. unpolarized light falls on them. what fraction of the light intensity is transmitted?

Match each type of lever with the correct diagram. 1. first-class 2. third-class 3. second-class

Apoint charge +q is at the origin. a spherical gaussian surface centered at the origin encloses +q. so does a cubical surface centered at the origin and with edges parallel to the axes. select "true" or "false" for each statement below. the electric flux through the spherical surface is greater than that through the cubical surface. suppose (for this statement only), that q is moved from the origin but is still within both the surfaces. the flux through both surfaces remains unchanged. the area vector and the e-field vector point in the same direction for all points on the spherical surface. the e-field at all points on the spherical surface is equal due to spherical symmetry. the flux through the spherical gaussian surface is independent of its radius.