A pencil is rolled off a table of height 0.35 m. If it has a horizontal speed of 2.1 m/s, how long does it take the pencil to reach the ground?

1) Kind of motion: horizontal launch

2) Formulas:

y = yo - Vo, y * t - g*t^2 / 2

yo = 0.35 m

g = 9.8 m/s^2

Vo, y = 0 (this is the pencil does not have initial vertical speed)

The time to reach the ground does not depend on the initial horizontal speed

3) Calculations

y = 0

=> 0 = 0.35 m - 9.8 m/s^2 * t^2 / 2

=> t^2 = 0.35 m * 2 / 9.8 m/s^2 = 0.0714 s^2

=> t = √ (0.0714 s^2) = 0.27 s

Answer: 0.27 s