Let's start by converting to m/s. There are 3600 seconds in an hour and 1000 meters in a kilometer, meaning that 72km/h is 20m/s.
Since the car starts at rest, you can write the following equation:
Now that you have the acceleration, you can do this:
Once again, there is no initial velocity:
Hope this helps!
true is the correct answer
grav force prop 1/r squared 2r all squared is 4rsquared 1/4rsquared quartered