A football running back of mass 90 kg moving at 5 m/s (positive direction) is tackled head on by another player of mass 120 kg running -4 m/s. They stick together. What is their final combined speed and direction (negative or positive sign)?

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.)

What property is a characteristic of a substance that can be observed and does not change the identity of the substance

If element x has 99 protons how many electrons does it have