# Centrifugal Force in a car

1. Aug 15, 2013

### Cromptu

Hello! I have some doubts regarding centrifugal force..
Imagine yourself in a car which is taking a sharp turn. You tend to fall to the other side ( if the car door is open you'd fall out of the car) Is this because of inertia which opposes the sudden change in motion or is it because of centrifugal force?

Thanks :)

2. Aug 15, 2013

### Staff: Mentor

You are correct except insofar as you are trying to separate things that are not separate.

From the reference frame of the ground, your inertia keeps you moving forward while the car accelerates away from you. Viewed from the rotating frame of the car, we call that centrifugal force.

3. Aug 16, 2013

### namanjain

A very mighty question, was asked in my olympiad THIS problem
so

let this be FBD in reference frame of car (comical i know but no matter)

→ centrifugal force
(car on a turn)
this centrifugal force pulls you out reference of car.

while inertia pulls you in front direction

4. Aug 16, 2013

### D H

Staff Emeritus
The answer is "yes". It's not an either-or kind of question.

From the perspective of an inertial observer, the answer is momentum. The answer is not momentum from the perspective of an observer fixed with respect to the turning car; your momentum is zero from this perspective. This is a non-inertial frame, so fictitious forces such as the centrifugal force appear to arise.

5. Aug 17, 2013

### namanjain

Actually the question doesn't clears in itself fall in front side or out of car

but still i perceive ans centrifugal force

6. Aug 17, 2013

### D H

Staff Emeritus
Try again, namanjain, but this time please use complete sentences and please don't use text speech.

You can't always use centrifugal force to explain why the passenger tends to fly out of the car as the car turns a corner. There is no such thing as the fictitious centrifugal force from the perspective of an inertial observer. This fictitious force isn't real. All that's needed to explain this phenomenon is momentum.

From a purely Newtonian point of view, asking what happens from the perspective of an observer fixed with respect to the turning car is a nonsense kind of question. Strictly speaking, Newton's laws of motion only pertain to inertial frames. The modern view of Newton's first law is that it is a test of whether the other two laws apply.

After Newton, physicists found that Newton's second law can be used in a non-inertial frame with the invention of various fictitious forces such as the centrifugal force. These fictitious forces are not real. They are invented forces that let us use F=ma to describe behavior. These fictitious forces can be extremely useful (challenge: describe the weather from the perspective of an inertial frame), but they are fictions nonetheless.

7. Aug 17, 2013

### bgq

Actually both are equivalent. The centrifugal force is a fictitious force (not real force), that you feel of it due to your inertia.

8. Aug 17, 2013

### D H

Staff Emeritus
You do not feel the fictitious force, you do not feel inertia (better said: momentum). You "feel" real forces. Except gravitation, of course. You don't feel that, either.

9. Aug 17, 2013

### bgq

The word "feel" seems to be ambiguous in physics I mean that you feel you are going to fall from the car, so you think there is a force pulling you out
This recall me of the hypothetical experiment of upward accelerating elevator in the space where you feel (think... whatever) that a force pulls you down.

10. Aug 17, 2013

### rcgldr

What you feel is a force from the seat and seat belt pulling you inwards. Your brain interprets this as something like gravity trying to pull you out of the car.

11. Aug 17, 2013

### bgq

What if you don't use the seat belt and the door of the car is removed, so you fall from the car? What do you feel in this case?

12. Aug 17, 2013

### A.T.

The concrete.

13. Aug 17, 2013

### A.T.

We don't feel forces. We feel deformations of body parts. Inertial forces and uniform gravity don't cause deformations.

14. Aug 17, 2013

### PhanthomJay

you feel the friction force between your seat and body. It keeps you moving on a turn without sliding, unless the turn is too sharp or speed too high, in which case the friction force is not enough to provide the required centripetal inward force to keep you moving with the car in its turn, so you instead move on a path tangent to the curve as you exit, in a straight line relative to the ground.

15. Aug 18, 2013

### bgq

:thumbs:

16. Aug 30, 2013

### namanjain

centrifugal force is just a pseudo force so why are you considering inertial reference frame, it's for sure the moving car (non inertial)

sorry : late reply!!!!!!!:tongue: