Why did the magnitude of the Doppler shift increase as the velocity of the sound source increased, but decreased as the velocity of sound increased

Asmall metal bar, whose initial temperature was 10° c, is dropped into a large container of boiling water. how long will it take the bar to reach 70° c if it is known that its temperature increases 2° during the first second? (the boiling temperature for water is 100° c. round your answer to one decimal place.) sec how long will it take the bar to reach 98° c? (round your answer to one decimal place.)

Which law represents the thermodynamic statement of the conservation of energy of a system? a. the fourth law b. the first law c. the second law d. the third law

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.