Ball Upwards.js

/*
You throw a ball vertically upwards with an initial speed v (in km per hour). The height h of the ball at each time t is given by h = v*t - 0.5*g*t*t where g is Earth's gravity (g ~ 9.81 m/s**2). A device is recording at every tenth of second the height of the ball. For example with v = 15 km/h the device gets something of the following form: (0, 0.0), (1, 0.367...), (2, 0.637...), (3, 0.808...), (4, 0.881..) ... where the first number is the time in tenth of second and the second number the height in meter.

Task
Write a function max_ball with parameter v (in km per hour) that returns the time in tenth of second of the maximum height recorded by the device.

Examples:
max_ball(15) should return 4

max_ball(25) should return 7

Notes
Remember to convert the velocity from km/h to m/s or from m/s in km/h when necessary.
The maximum height recorded by the device is not necessarily the maximum height reached by the ball.
*/
function maxBall(v0) {
  const v = v0 * 1000 * 10 / 3600;
  return Math.round(v / 9.81); 
}