Yenka Motion lets you experiment freely with forces and motion, with control over a wide range of parameters. It covers the same motion topics as were found in Crocodile Physics.
Add balls, blocks and carts, position them as you wish, and drop, accelerate or collide them.
Define parameters like mass, elasticity, coefficient of friction, dimensions, velocity and driving force, and add your own images to give context.
Attach rods and springs to investigate simple pendulums, spring oscillations, Hooke's Law and rotational motion.
Add gravity to your simulations - you can set the strength of this field, and also the elasticity and friction of the ground.
You can graph the motion of your parts - plot a wide range of quantities, like velocity, momentum, kinetic and potential energy, or acceleration.