Force and Motion - Car going over a hill

Click For Summary

Homework Help Overview

The problem involves a stuntman driving a car over the top of a hill, modeled as a circular arc with a specified radius. The focus is on determining the maximum speed at which the car can travel without losing contact with the road due to the forces acting on it.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster expresses uncertainty about how to approach the problem. Some participants suggest using the concept of centripetal force and its relationship to speed, while others question the assumptions about the forces involved, particularly regarding how gravity interacts with the centripetal force at high speeds.

Discussion Status

Participants are exploring the relationship between centripetal force and gravitational force in the context of circular motion. There is some clarification regarding the role of gravity at the top of the hill, but the discussion remains open with various interpretations being considered.

Contextual Notes

The problem is framed within the constraints of a homework assignment, which may limit the information available to participants. The original poster's confusion about the forces involved indicates a need for deeper exploration of the concepts of circular motion and forces.

Shatzkinator
Messages
52
Reaction score
0

Homework Statement


In Figure 6-58, a stuntman drives a car (without negative lift) over the top of a hill, the cross section of which can be approximated by a circle of radius R = 211 m. What is the greatest speed at which he can drive without the car leaving the road at the top of the hill?


Homework Equations


Ac = mv^2/R
fnet = ma


The Attempt at a Solution


I honestly have no idea how to tackle this problem. Help?
 
Physics news on Phys.org
It is circular motion. Recall that a "centripetal force" is required to hold an object in circular motion. You must use that formula and be aware of what force is providing the centripetal force. That force will become too small when the speed gets too high. Set them equal and solve for the speed.
 
Delphi51 said:
It is circular motion. Recall that a "centripetal force" is required to hold an object in circular motion. You must use that formula and be aware of what force is providing the centripetal force. That force will become too small when the speed gets too high. Set them equal and solve for the speed.

I don't understand. First of all, the force causing the motion is the car itself moving up the hill. If the formula you're talking about is Fc = mv^2/R, then I don't see how the force will become small when the speed is high. They are directly proportional so the force would increase as the speed increases. Please clarify... thanks =)

edit: got the answer, Fg is the force = mg = mv^2/R
 
Last edited:
Congrats! Yes, gravity provides the centripetal force right at the top of the hill.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
6K
  • · Replies 10 ·
Replies
10
Views
6K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 7 ·
Replies
7
Views
6K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 12 ·
Replies
12
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 8 ·
Replies
8
Views
8K
  • · Replies 6 ·
Replies
6
Views
19K