When a flat slab of transparent material is placed under water, the critical angle for light traveling from the slab into water is found to be 60°. what will the critical angle be if the slab is surrounded by air? take the index of refraction for water to be 1.33. d) 45.6 c) 44.2 e) 47.3 a) 40.6 b) 42.5

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".