Ethan and Alex run a 400-meter race. • Ethan takes m seconds to cover 400 meters and Alex
takes n seconds to cover 400 meters.
• Alex takes 20 seconds more than half the time
Ethan takes to cover 400 meters.
Enter the equation to show that Alex takes 20 seconds
more than half the time Ethan takes to cover 400 meters.

Ateacher attaches a ball to a meter long string and whirls it around in a horizontal circle at constant speed. the teacher explains that the string is what makes the ball go in a circle. why is the string necessary? a) the string is needed to apply a torque to the ball. b) the string is needed to push on the ball to get it up to speed. c) circle motion requires an inertia which is provided by the string. d) circle motion requires a force to give it a centripetal acceleratio