Hi, I am a pre-AP Physics student who tends to think too muchabout physics (to g

Question

Hi, I am a pre-AP Physics student who tends to think too muchabout physics (to give myself some credit, I have one of thehighest grades in our class). While learning about forces andthen centripetal force, I found something in the book that seems torefute it's earlier statements. I don't feel like I havediscovered a major flaw in physics, but rather feel my textbook hasnot explained well. Thank you for helping in advanced! Then we went into centripetal forces on a banked curve. Force centripetal = Force pointing toward center plus forcefriction Using the earlier chapter, I would assume that Force frictionwould be Fn or mgcos wheremgcos=Fn. However, the chapter told me mg =Fncos because in banking the car's weight must beheld up by that force. Makes sense. But if I usemg=Fncos and change it to mg/cos =Fn. Set that equal to the other equationmgcos=Fn, I get mgcos=mg/cos, orcos2 = 0. This is only true when cos=0 degrees. Yet the book uses the second equation frequentlyafterwards. I don't think I have discovered anything, butrather just encountered a difference in the underlying principlesof inclined planes and banking that the book didn't bother to gointo. Could someone explain? Thanks!

Explanation / Answer

FN = m g cos     only if the car is not moving As the speed of the car increases then FN will alsoincrease to provide the necessary centripetal force and in that situation FN sin = mv2 / R and FN cos = m g Dividing equations you get tan = v2 /(R g) FN = m g cos does not hold whenthe car is moving around the curve because the requiredcentripetal force is included in FN Remember the basic equation is F = m a and FNsin = m v2 / R where a =v2 / R Remember the basic equation is F = m a and FNsin = m v2 / R where a =v2 / R

Related Questions

Navigate

• Browse (All)
• Browse H
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.