Atrain collided into a car stalled on the tracks with a force of 12,500 n over the course of seconds. what is the change of momentum of the car?

Ihave a density of 1.61g/cm^3 and a mass of 28g. find the missing value

A10nc charge sits at a point in space where the magnitude of the electric field is 1500 n/c. what will the magnitude of the field be if the 10 nc charge is replaced by a 20 nc charge? assume the system is big enough to consider the charges as small test charges.

What are the necessary conditions for fusion?