# Question about circular motion

• physicsdude12
In summary, the conversation discussed the application of circular motion in road curves and the relationship between centripetal force and velocity. It was explained that friction between the tires and the road allows the car to maintain a tractive force and be steered on a curve. When the road is banked, there is a horizontal component of force applied by the road. The relationship between centripetal force and velocity was also discussed, with the understanding that when the velocity is doubled, the centripetal force quadruples. This can be compared to linear kinetic energy, where doubling the velocity quadruples the kinetic energy but only doubles the momentum. Overall, the conversation clarified the reasons for a car running off a road when going too fast and the relationship between
physicsdude12
Hey everyone,

I'm having trouble understanding a few aspects in circular motion and specifically in the application of road curves.

Would it possible for someone explain why a car runs off a road when it is going to fast? Basically, i know that a velocity greater than the optimal velocity for a banking angle causes the car to move off in a tangent, but I'm having trouble understanding why this occurs.

Also, the relationship between centripetal force and velocity (centripetal force directly proportional to velocity squared) has confused me even more. Basically, that relationship says that if the velocity doubles, the centripetal force quadruples! This can't be true because when a car is going very fast around a curve, the centripetal force is not enough to keep it in circular motion.

If someone could help me, i would greatly appreciate it.
Thanks,

Also, i am very sorry for my English, it is not the greatest :S

On a surface, friction between the tires and the road keep allow the car to apply a tractive force. On a curve without banking the frictional force allows the car to be steered (turned) in the curve. With banking (inward), there is a horizontal component of force applied by the road.

See - http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/carbank.html

and http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html

Since Fcentripetal = mv2/r, when v is doubled, Fcentripetal is quadrupled.

Similarly, for linear kinetic energy, KE = 1/2mv2, when v is doubled, the kinetic energy is quadrupled, but the momentum, mv, only doubles.

Last edited:
Thank you very much for your help! :!)
This was really confusing me

## 1. What is circular motion?

Circular motion is a type of motion where an object moves along a circular path at a constant speed.

## 2. What causes an object to undergo circular motion?

Circular motion is caused by a combination of centripetal force and the object's inertia.

## 3. How is circular motion different from linear motion?

Circular motion involves a change in direction, while linear motion involves a change in position.

## 4. What are some real-life examples of circular motion?

Some examples of circular motion include a car moving around a roundabout, a spinning top, and a satellite orbiting the Earth.

## 5. What is the role of centripetal force in circular motion?

Centripetal force is the inward force that keeps an object moving in a circular path. It is necessary to counteract the object's tendency to move in a straight line due to its inertia.

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