Which is larger, 12 kilometers or 7.5 miles? Show you’re work plz ASAP

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

True or false when elements combine to form a mixture, the resulting chemical properties may be very different from those of the elements that make it.

What are the similarities & differences between a thermistor and a light dependent resistor in physics?