
William W. answered 01/27/22
Experienced Tutor and Retired Engineer
The potential energy of the spring (US) is calculated from:
US = 1/2kx2 where k is the spring constant and x is the distance the spring is pulled back.
After the dart is released, all that energy is converted to kinetic energy as the dart leaves the spring/gun. Kinetic energy is calculated as 1/2mv2. Since energy is conserved, the spring potential energy equals the kinetic energy so:
1/2kx2 = 1/2mv2
You can just plug in the numbers and solve for "v".