Question

An autographed baseball rolls off of a 0.93 m high desk and strikes the floor 0.56 m away from the desk. How fast was it rolling on the desk before it fell? The acceleration of gravity is 9.81 m/s^2. Answer in units of m/s.

Answer 1

First of all, how long does it take it to fall 0.93m to the floor ?

Distance falling from rest = (1/2) · (g) · (T²)   <== memorize this formula

(0.93 m) = (1/2) (9.8m/s²) (T²)

Divide each side by (4.9 m/s²) :  T² = (0.93/4.9)  =  0.1898 s²

Square root each side:  T to hit the floor = 0.436 second

It got 0.56m away from the desk horizontally in 0.436 sec.

Speed = (distance) / (time)    <=== memorize this formula

Speed = (0.56 m) / (0.436 sec)

Speed = 1.28 m/s