In standard household wiring, parallel wires about 1cm apart carry currents of about 15A . What’s the force per unit length between these wires?

Abumper car with a mass of 250 kg is traveling at a speed of 4 m/s. this bumper car collides and sticks to a second bumper car with a mass of 250 kg, which is initially at rest. what is the final speed of these two bumper cars after the collision, assuming they remain stuck together?