When the window is closed, the switch on the electric circuit of the alarm is moved to the "off" position. When the window is opened, the switch on the electric circuit of the alarm is moved to the "on" position.

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?