How long will an object thrown vertically upward with a velocity equal to g take to fall back?

Correct answer: d 2 s

The time of flight is T = 2u/g, which for u = g is 2 s. The rise and the descent take equal times.

Why the other options are wrong

• a 0.5 s: 0.5 s comes from no correct step. With u = g the rise takes u/g = 1 s and the fall takes 1 s as well.
• b 1 s: 1 s is only the time of the rise (u/g). The question asks for the whole time until it falls back, rising and coming down both.
• c 1.5 s: 1.5 s is the rise of 1 s plus half of the descent. The descent takes exactly as long as the rise.