What is the role of centripetal force in circular motion?

[ThomasMagnus]

Hello,

I am currently studying circular motion, and I would like to know if the statements I have made below are correct.
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The centripetal force is the sum of all forces acting on an object in circular motion. **Centripetal force itself is not a force.

When a car is traveling around a turn, the centripetal force will be equal to the F_F (points toward center of circle) acting on the car.

When riding a bicycle, why must you learn inward while turning?

When you round a curve, the tires exert an inward force (friction against the tires) on the bicycle to make it move in a curved path. This inward force causes the rider to be pushed inwards.

Thank you

 

[Drakkith]

The centripetal force is the sum of all forces acting on an object in circular motion. **Centripetal force itself is not a force.

Can you explain why you think this? What other forces are involved?

When riding a bicycle, why must you learn inward while turning?

Can you turn a bike and not lean over? What happens if you can? Why do you think that?

I wrote a whole explanation, and then realized this was in the homework section and had to edit it lol.
Per the rules I can't just give you the answers. But I can help!

 

[ashishsinghal]

The centripetal force is the sum of all forces acting on an object in circular motion. **Centripetal force itself is not a force.

No, centripetal is the sum of all forces acting radially in a circular motion. Centripetal force itself is not a force.--Thats right.

When a car is traveling around a turn, the centripetal force will be equal to the F_F (points toward center of circle) acting on the car.

Thats right. But other forces may also be present depending on situation.

When riding a bicycle, why must you learn inward while turning?

When you round a curve, the tires exert an inward force (friction against the tires) on the bicycle to make it move in a curved path. This inward force causes the rider to be pushed inwards.

This doesn't answer why you need to lean. Friction would occur even if you do not lean. And the friction acts towards the center because you turn the wheel. You lean to counter the torque created due to centrifugal force. If you do not lean your bike will fall down.

 

[ThomasMagnus]

Could the bike question be explained by Newton's first law? --your body tends to want to travel in a straight line, so you have to correct it by leaning.

Thanks!

 

[ashishsinghal]

No, I think you got it wrong. There are two motions we are talking about. One is the circular motion of the bike and the other the motion of our toppling due to centrifugal torque.

 

[ThomasMagnus]

"The torque created by centrifugal force"

Where is the centrifugal force coming from?

Thanks

 

[ThomasMagnus]

Is this centrifugal force a reaction to the centripetal force (in this case Ff)?

Appreciate the help! :)

 

[ashishsinghal]

see, when you consider motion in a non inertial (accelerating) frame, a force acts on the object you are analyzing. This force is called pseudo force. If you are analyzing an object of mass m and acceleration of non inertial frame is a, then pseudo force is equal to -ma. ie it acts opposite to your acceleration.
In circular motion you are analyzing the bike in a frame which is also doing circular motion along with the bike. So its acceleration is v^2/r radially inwards. So the pseudo force on bike = mass of bike * v^2/r radially outwards. This force is called centrifugal force.

 

[ThomasMagnus]

The way you explained it, it seems that the centrifugal force is a reaction to the centripetal force (Their equal in magnitude). Is this true?

http://en.m.wikipedia.org/wiki/Centrifugal_force

Thank you! :)

 

[ThomasMagnus]

OK so I have been posting on the forums trying to figure this out, and I think I more-less get it.

Can we say that the bike is leaning inward because the centripetal force is acting toward the center? (in simple terms)

Thanks

 

[ashishsinghal]

centripetal force is not a physical force which can act. forces acting radially constitute it. In this case what do you think is the centripetal force? How do you think leaning is influenced by it?

 

[cupid.callin]

Hi Thomas

Consider this pic

the Big line is the Cycle+Rider and rest are forces as shown

If you take the center of circular motion ... there will be a pseudo centrifugal force acting ... (as shown by mv²/R)

Taking net torque about point A ...

only mg and centrifugal force have torque ... now if you don' t lean inward ... the torque of centrifugal force will make you fall outward.

So you must lean inward such that torque of centrifugal force is canceled by torque of mg ...also if you calculate the angle,
tanδ = v²/Rg