A room measuring 21 m by 18 m and 13 m high has to be lighted by four lighting fixtures suspended 3 m from ceiling. The ceiling points are symmetrically placed on the two diagonals so that each point is 7 m from the center of the ceiling. An illumination of 12 lux apart from any effect due to the walls and ceiling is required on the center of a table 3 m high placed at the center of the room. What luminous intensity must each unit give in direction necessary to produce this result?

What defines the mass number of an isotope? a. the sum of the neutrons and protons b. the sum of the neutrons and electrons c. the number of neutrons d. the number of protons

Aprojectile is launched horizontally 10m above the ground and with an initial velocity of 15 m/s. a) sketch the trajectory using an appropriate coordination system. b) how long for the projectile to reach the ground. c) how far did projectile travel horizontally before striking the ground. d) determine the projectilex & y position at t-1.3s e) determine the magnitude and direction of projectile velocity at t= 1.3s f) determine the magnitude and direction of projectile acceleration at t-1.3s

Power can be defined as a. the distance over which work was done. b. how much work can be done in a given time. c. all the work in an given area. d. the energy required to do work.