How do I rip the shorts?

Make a score with scissors while they're on a hard surface (and off your body). After several scores along the same line, they should be turning white. Using a ruler can help keep them straight if you want. Make a small snip in the middle of the line (away from the seams) and then hook your fingers in and pull. This will take some effort and strength. If you want to remove the leg then you can cut across the seams, as you will not be able to rip them. To rough up the edge pieces that you cut with the scissors, use the inside edge of the scissors to rub them as if you were sanding a piece of wood.