Kinectimals

"Jumped 3 yards with an RC car"

Easy to get. Either near the treehouse when you first get the RC car or the first race, go full speed (arms out ahead of you) and jump (jump) to get some distance.

STUNTMAN - I did this in cherry blossom grove,there is a large jump on the R.C track,jump over this and you will get the cheevo very easily.

Stuntman
"Jumped 3 yards with an RC car."

I found this alot easier to do in Fiddler's Beach (second place you unlock), in Free Play. There will be a small pile of sand and if you ramp up it and jump at the same time the cheevo should pop right when you hit the ground.

This achievement requires you to jump 3 yards (in a single jump) while driving an RC car. While progressing through the game you will learn that holding your arms out like you are driving a real car will make your RC car move forward. While moving forward if you physically jump (yourself), your car will jump too.

As you find new parts of the map you will come across Cherry Blossom Grove. In this part of the map there is an RC Car race challenge. In the middle of this challenge track is a wooden bridge.

As you compete in the race, jump as you approach the top of the ramp on this bridge and you will easily net the 3 yards required to complete the achievement.

This is not the only place where you can get the achievement, it is simply an easy place to get it, and it's where I got it.

In reality, any place (freeplay or challenge) where you can use an RC car and find a little launching pad can be used, but your results will vary based on how big that obstacle launching pad is etc.

Good luck and safe driving! :-)