Avertical spring (ignore its mass), whose spring stiffness constant is 880 n/m, is attached to a table and is compressed down 0.170 m. (a) what upward speed can it give to a 0.300 kg ball when released?

When the spring is compressed, the potential energy stored in the spring is:

where k=880 N/m is the spring constant and  is the compression of the spring. By using these numbers, we get


When the spring is released with the ball over it, all the potential energy is converted into kinetic energy of the ball:

So by using m=0.300 kg, and re-arranging the formula, we can calculate the velocity of the ball:

Rain is pulled by gravity which is a non contact force