Personal Training Session

See this picture above. I don't know what this is called but when i workout I use it.  Read below to hear a funny story about this "half ball thing"

Today I was on my own to do some personal training.  I meet with my trainer 2x a week, but he gave me this homework to do twice before we would meet up again.
5 reps of turkish get ups w/ 20lb keetle
12 Kettlebell swings (25-35lb)
12 ovehead preses w/ 15-20lb keetle ball
12 step ups with 15lb keetle ball in each hand (This was the very hardest exersize b/c the step was so high)
12 burpees with a half stability ball
12 Medicine ball slams (10lbs)
12 Single leg RDL w/ 25 lbs in same hand as leg lifts
12 reverse lunges w/ 20lb
12 sumo squats w/35lb
1 minute plank on stability ball
ALL THESE 3 TIMES!

So doing a burpee involves a pushup and then standing straight up and doing one big jump.  It's not so hard, except when down quickly 10 times in a row!  Well my training had me doing a jump on the ball pictured above after the pushup.  Well  everyone take not to not put in on a hardwood floor when doing that move.  Just do it on the black mat just like the training had you do.  Did you guess what happened when I went to jump on this "thing".  Yes, it went flying forward across the floor and I went flying backwards and down on my butt.  Luckly I wasn't hurt, and some bystanders got a good laugh. 
Everyone says I am funny, the thing is I don't do it on purpose.