Learn the science
No special circular-motion force
An object has no separate force called 'centripetal force' in addition to all other real forces. The phrase 'centripetal force' is shorthand for the net inward component of actual interactions. On a horizontal unbanked road, the tire-road static friction is the principal horizontal inward force. For an ideal horizontal string-and-puck setup, tension can supply the radial force.
Choose the body, then list agents
For a car on a level road, gravity pulls down and the road's normal force acts up; those can balance vertically. The road's sideways friction on tires may then contribute net inward force. A free-body diagram of the car includes actual agent-on-car forces. Do not add an extra inward force called F_c if you have already drawn the real inward interaction—it would double count.
A banked turn is a different model
On a banked road, the normal force can have a radial component; friction can also contribute depending on speed and design. The simple flat-road calculator here deliberately excludes banking, aerodynamic effects and changing load distributions. Never use its estimates as safe road-speed advice or a real structural design certificate.
Model independent of physical demonstrations
A numerical laboratory can assign mass, speed, radius and a proposed force mechanism without anyone swinging objects or driving. In a real experiment, measuring force direction accurately would require appropriate sensors and supervision. Today's visual model provides vectors and labeled synthetic values, not observations from real vehicles.