A ball fall off at an speed of 20khr at the distance of 10cm, find the mass?

To find the mass of the ball, we can use the formula for kinetic energy:

KE = 0.5 * m * v^2

Where:
KE = Kinetic energy
m = Mass of the ball
v = Speed of the ball

First, we need to convert the speed from km/hr to m/s:
20 km/hr = 20 * 1000 m / 3600 s = 5.56 m/s

Now, we can plug in the values into the formula:

KE = 0.5 * m * (5.56)^2
KE = 0.5 * m * 30.94
KE = 15.47m

Next, we can calculate the potential energy of the ball at a height of 10 cm:

PE = m * g * h
PE = m * 9.8 * 0.1
PE = 0.98m

Since the ball falls off, the potential energy is converted into kinetic energy:

KE = PE
15.47m = 0.98m
m = 15.47 / 0.98
m = 15.78 kg

Therefore, the mass of the ball is 15.78 kg.

The question lacks sufficient information to determine the mass of the ball. The provided data only includes the initial speed and distance, which are not enough to calculate the mass. Additional information, such as the height from which the ball was dropped or the time it took to fall, would be needed to determine the mass.