23. Christina wanted to know whether the eating behavior of goldfish is affected by music. She set up a fish tank. Every day, she played music for the fish and measured how much the fish ate. What is Christina

missing from this experiment?

A. a control group

B. a measurable result

C. a dependent variable

D. different types of fish

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".

What is the period of a wave traveling 5 m/s if its wavelength is 20 m/s

Adistance-time graph indicates than an object moves 100 m in 4 s and then remains at rest for 6 s. what is the average speed of the object?