French help please!!

Karen is running forward at a speed of 9 m/s. she tosses her sweaty headband backward at a speed of 20 m/s. the speed of the headband, to the nearest whole number relative to a stationary observer watching karen

4. a 75.0 g piece of ag metal is heated to and dropped into 50.0 g of water at the final temperature of the mixture is what is the specific heat capacity of silver? 5. a 465 g chunk of iron is removed from petrucci, ralph h.. general chemistry (p. 290). pearson education. kindle edition.

Which of these has some mechanical energy? a. an atom b. heat inside earth c. a book on a shelf d. the fire from a lit match