. A girl runs and jumps horizontally off a platform 10m above a pool with a speed of 4.0m/s. As soon as she leaves the platform, she starts flipping, spinning with a constant angular acceleration of 15.0rad/s2. How many revolutions does she make before hitting the water? (Note that maintaining constant angular acceleration in the air is not realistic, but let’s do it here anyway.)\

2.39 revolutions

Explanation:

As she jumps off the platform horizontally at a speed of 10m/s, the gravity is the only thing that affects her motion vertically. Let g = 10m/s2, the time it takes for her to fall 10m to water is

Knowing the time it takes to fall to the pool, we calculate the angular distance that she would make at a constant acceleration of 15 rad/s2:

As each revolution is 2π, the total number of revolution that she could make is: 15 / 2π = 2.39 rev