If the slope of an object's position versus time graph is decreasing, what does this indicate about the velocity of the object?

Amoving electron has kinetic energy k1. after a net amount of work w has been done on it, the electron is moving one-quarter as fast in the opposite direction. (a) find w in terms of k1. (b) does your answer depend on the final direction of the electron's motion?

If anyone who can me with this hw? i would really appreciate it

Why is the use of carbon-14 limited