Why Is the Minimum Speed Where the Seat Exerts No Force?

In summary, the minimum speed will be at the point where the seat doesn't have to exert any force on you. This defines the point where you just start to lose contact with the seat--in other words, it's the point where you start to fall out of the seat.
  • #1
ThomasMagnus
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Roller Coaster--Circular Motion

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I have a few questions about the way this question was done. The instructor said: "The minimum speed will be at the point where the seat doesn't have to exert any force on you".

This doesn't make sense to me. Why will the minimum speed be at this point?

Thanks
 
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  • #2


ThomasMagnus said:
Why will the minimum speed be at this point?
That defines the point where you just start to lose contact with the seat--in other words, it's the point where you start to fall out of the seat.

You do realize that the faster you go, the more you are pushed against the seat and thus the greater the normal force?
 
  • #3


Doc Al said:
You do realize that the faster you go, the more you are pushed against the seat and thus the greater the normal force?

This is where I am mixed up.

At the top of the loop, the forces acting on the the person will be fg and fn and they are in the same direction (downwards)

Since the centripetal force is the sum of these then: Fc=Fg+FN

If both forces are acting downwards, what is pushing you into your seat? Why won't you fall out?

Thanks (I'm new at this :) )
 
  • #4


ThomasMagnus said:
At the top of the loop, the forces acting on the the person will be fg and fn and they are in the same direction (downwards)
True. But realize that while fg is fixed (it's your weight), fn is not. fn depends on the speed.

Since the centripetal force is the sum of these then: Fc=Fg+FN
OK. Note that Fn and Fc will change with the speed.

If both forces are acting downwards, what is pushing you into your seat? Why won't you fall out?
Realize that you are moving fast. Without the seat there, you'd go shooting off into the air. You need forces pushing you down, not up. (You can think of it as your inertia pushing you into the seat.)

Fn is a measure of how hard the seat has to push down on you to keep you from going straight. If you go too slow, the seat won't have to push you at all--you'll start falling.
 
  • #5


Thank you, I think I am catching on.

Why would you need forces acting down if the car is upside down? Wouldn't you need them upwards to keep you in the seat?
 
  • #6


Would it be because on the way up the loop, your body is going to want to travel in a straight vertical path according to Newton's first law, and thus the seat is going to have to correct that (ie push down)?
 
  • #7


ThomasMagnus said:
Would it be because on the way up the loop, your body is going to want to travel in a straight vertical path according to Newton's first law, and thus the seat is going to have to correct that (ie push down)?
Exactly!
 
  • #8


Great.

Thank you very much for your help! :smile:
 

FAQ: Why Is the Minimum Speed Where the Seat Exerts No Force?

What is circular motion in relation to roller coasters?

Circular motion refers to the motion of an object along a circular path. In roller coasters, this is seen when the train moves along the track in a circular loop or curve.

How does circular motion affect the experience of a roller coaster ride?

Circular motion can affect the experience of a roller coaster ride by creating thrilling moments of acceleration and deceleration, as well as changes in direction. This can contribute to the sense of excitement and adrenaline that riders feel.

What factors influence the circular motion of a roller coaster?

The circular motion of a roller coaster is influenced by several factors, including the design of the track, the speed of the train, and the force of gravity. In addition, the weight and distribution of the riders can also affect the circular motion.

What is centripetal force and how does it relate to roller coaster circular motion?

Centripetal force is the force that pulls an object towards the center of a circular path, keeping it in motion along that path. In roller coasters, this force is provided by the track and wheels, which allows the train to maintain its circular motion.

How do engineers design roller coasters to ensure safe and enjoyable circular motion?

Engineers use a variety of calculations and simulations to design roller coasters that provide safe and enjoyable circular motion. This includes considering the forces acting on the train, as well as factors such as the height, speed, and shape of the track. They also conduct rigorous testing to ensure the safety and comfort of riders.

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