Why two fluorine atoms are bonded by covalent bond?

Ineed the answers for these promblems i have

In a heat engine if 1000 j of heat enters the system the piston does 500 j of work, what is the final internal energy of the system if the initial energy was 2000 j? 1. write the equation 2.list out your known variables 3.plug the numbers into the equations 4.solve 5.write your solution statement that includes initial energy and final

Compare the horizontal displacement of the two balls as they travel to the ground. what do you observe?