Combined momentum before collision

Atrain departs from its station at a constant acceleration of 5 m/s. what is the speed of the train at the end of 20s?

Does work output exceed work input when a machine is used? a) yes, it does, as machines create energy. b) it depends on the type of machine used. c) no, it doesn’t, as machines are inefficient. d) no, it doesn’t, as machines cannot create energy.

Why is the use of carbon-14 limited