Kinematics..

As we all know is the study of motion of particles. The motion of particles can be described in different forms...

linear , planar , cartesian coordinates , polar coordinates and normal and tangential coordinates

I'm having trouble understanding the last two... I mean if a particle's motion is to be described in a linear form then

position = s , velocity = Δ s /Δ t , acc= Δ v/Δ t ... ect and the same applies to planar form ( i dont quite understand the difference )

The other forms have a bit more complex way....

How do i use these concepts to answer the following questions ?

1.A car is following a path round a corner with a constant radius of 80m. If the maximum lateral acceleration that can be generated by the tyres is 1.2g, what is the maximum speed the car can follow the path?
What is the maximum speed if the radius of the corner is 180m?


2.A linear actuator is pivoted at one end to move in a plane. If the actuator is rotating at a constant rate of 40 deg/s, and the actuator length is decreasing at a constant rate of 100mm/s, what is the velocity of the end of the actuator when the actuator length is 750mm?
What is the magnitude and direction of the velocity relative to the radial direction?

Help very much appreciated.. thanx