Loop related to Circular motion

Click For Summary

Homework Help Overview

The discussion revolves around a physics problem involving circular motion, specifically a skateboarder navigating a loop. The parameters include the radius of the loop, the weight of the skateboarder, and the height from which they start. The participants are exploring how to determine the necessary speed to complete the loop successfully and the height required for that speed.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the potential use of kinematics and conservation of energy principles. There are questions about the initial and final velocities, and whether the final speed at the top of the loop can be zero. Some suggest that the skateboarder must maintain a speed to counteract gravity.

Discussion Status

There is an ongoing exploration of different approaches, with some participants offering guidance on using energy conservation and centripetal acceleration. Multiple interpretations of the problem are being considered, particularly regarding the final velocity and the role of tension in the equations presented.

Contextual Notes

Participants are working under the assumption that friction is not a factor in this scenario. There is also a mention of an informal context, as the problem is derived from a practical example related to a stunt from a show.

Kikki:)
Messages
17
Reaction score
0

Homework Statement



The radius is 7ft, the diameter is 14ft, the person is 181lb and is 6ft 1in.

How fast does he have to start the loop to be successful all the way around?
How high does he have to start?
Don't need to apply Friction.

Homework Equations


Cetripetal Force? Flo Diagram?


The Attempt at a Solution



I'm not getting how to start or find it. I know possibly kinematics is involved with it.
 
Physics news on Phys.org
I also forgot to mention that it is a skate boarder going down a ramp and into a big loop, it was off of jackass, out teacher is made this equation from it by just estimating it. I'm mainly wanting to learn how to do the problems. :] So would you try to find the circumference first? So would the final speed be 0 ? I know that the gravity force is 9.8 m/s/s. A possible equation from kinematics would be final velocity= initial velocity + acceleration x time. But the problem is I would need to know the time.
 
Hi Kikki:) Welcome to PF! :smile:

I'd recommend using conservation of energy combined with the required centripetal acceleration to stay in a circular trajectory.

At the top the center of mass of the skater should have a speed high enough to match the centripetal acceleration, that is:
vf2 / r.

To achieve that he should have an initial speed dictated by conservation of energy, that is:
vi2 / 2 = vf2 / 2 + g h
 
I like Serena said:
Hi Kikki:) Welcome to PF! :smile:

I'd recommend using conservation of energy combined with the required centripetal acceleration to stay in a circular trajectory.

At the top the center of mass of the skater should have a speed high enough to match the centripetal acceleration, that is:
vf2 / r.

To achieve that he should have an initial speed dictated by conservation of energy, that is:
vi2 / 2 = vf2 / 2 + g h

But how do you exactly figure out the final velocity because I tried it as having it as zero. I also came up with a formula too that I think could work also related to yours.

v2=Tension + mg
 
Kikki:) said:
But how do you exactly figure out the final velocity because I tried it as having it as zero.

If the final velocity (at the top) would be zero, the skater wouldn't be going forward anymore, and fall straight down. Ouch! :smile:

He needs to have a speed high enough to neutralize gravity, that is:
vf2 / r = g
Kikki:) said:
I also came up with a formula too that I think could work also related to yours.

v2=Tension + mg

Huh? Don't know that one? :confused:

What is "Tension"?
The units don't match, that is, v2 is not a force like the others...

Apparently this is supposed to be a forces sum, but consider when it would be applicable and what the directions / signs should be... :wink:
 

Similar threads

Small bead - Circular loop Problem
  • · Replies 1 ·
Replies
1
Views
2K
Circular motion - ball in a loop
  • · Replies 19 ·
Replies
19
Views
4K
Loop problem with skier on ramp going into a loop-the-loop
  • · Replies 13 ·
Replies
13
Views
2K
Why Can't Conservation of Energy Be Used to Solve the Loop Problem in Physics?
  • · Replies 3 ·
Replies
3
Views
2K
Simulated circular motion on a roller coaster
  • · Replies 5 ·
Replies
5
Views
3K
Circular Motion With Constant Angular Acceleration
  • · Replies 3 ·
Replies
3
Views
3K
Electromotive force (EMF) of a circular loop wire
  • · Replies 3 ·
Replies
3
Views
2K
Gravity and uniform circular motion involving a loop?
  • · Replies 4 ·
Replies
4
Views
2K
Centripetal Force and circular motion
  • · Replies 3 ·
Replies
3
Views
2K
Uniform Circular Motion Inside a Sphere of Charge
  • · Replies 7 ·
Replies
7
Views
3K