Donkey kong country mine cart

How can I make a part in my game have a mine cart (anything realy) that when the player jumps inside it, the cart starts moving on a set path?

You can put a small invisible sprite inside the cart. When player is in collision with this sprite, start moving the cart.

You can also disable player's controls while the cart is moving and pin player to it.

dop2000 I'm wanting it to go downhill so would it have to be a physics item?

If the path is not a straight line, then yes, it would probably be easier to use physics.

If you don't want to deal with the wheel rotation, friction, revolution joints etc., you can use an invisible sprite with physics behavior. Push it downhill and then on every tick set your cart to that sprite position and angle.