A Doppler radar sends a pulse at 6.00x109 Hz. It reflects off clouds
moving away at 8.52 m/s. What is the
change in frequency in the echo?

What is the gravitational attraction between a dating couple whose centers of mass are 0.630 m apart if the boy weighs 715 n and the girl weighs 465 n?

Which of the following is part of the explanation or description of electromagnetic waves? (select all that apply) a. electrically charged molecules in a medium transfer their energy to nearby electrically charged molecules. b. a changing electric field causes a changing magnetic field. c. magnetic molecules in a medium transfer their energy to nearby magnetic molecules. d. a changing magnetic field causes a changing electric field.

According to the image below, which season is about to begin in the southern hemisphere? a. summer b. autumn c. winter d. spring