The table below show factors that affect sleep patterns in humans, with locations of sleep stimulants X and Y missing from the table. Stimulus Internal
or
External Response
Time of day X Lets the body know when it is time to go bed
Levels of chemical serotonin Y Tells the body it is sleepy or encourages alertness

What are X and Y?
A.
X is external; Y is internal

B.
X is internal; Y is external

C.
X and Y are external

D.
X and Y are internal

Follow these directions and answer the questions. 1. set up the ripple tank as in previous investigations. 2. bend the rubber tube to form a "concave mirror" and place in the ripple tank. the water level must be below the top of the hose. 3. generate a few straight pulses with the dowel and observe the reflected waves. do the waves focus (come together) upon reflection? can you locate the place where the waves meet? 4. touch the water surface where the waves converged. what happens to the reflected wave? 5. move your finger twice that distance from the hose (2f = c of c, center of the curvature) and touch the water again. does the image (the reflected wave) appear in the same location (c of c)? you may have to experiment before you find the exact location. sometimes it is hard to visualize with the ripple tank because the waves move so quickly. likewise, it is impossible to "see" light waves because they have such small wavelengths and move at the speed of light. however, both are examples of transverse waves and behave in the same way when a parallel wave fronts hit a curved surface.

Isla’s change in velocity is 30 m/s, and hazel has the same change in velocity. which best explains why they would have different accelerations? isla had negative acceleration, and hazel had positive. isla had a different time than hazel. isla had positive acceleration, and hazel had negative. isla went a farther distance than hazel.

The earth is constantly spinning on its axis, like you might spin a basketball on your finger. it is this spinning of the earth that causes