Unformatted text preview: Lecture 16
Feb 26, 2007 P112 Announcements
Prelim Review session
TBA Prelim on Thursday 7.30pm Bring:
Your own Formula sheet (8.5x5.5) Nongraphing calculator Pen, protractor, ruler
In past semesters students have regretted forgetting their protractor/ruler Agenda for today
Continuing with Circular Motion
Last lecture on forces! Rotating frame: nonintertial Loop the loop
A R B Loop the loop
Why does the ball stay in contact with the track at the top? Which factors determine if the ball stays in contact with the track? Loop the Loop
What is the minimum speed such that the ball stays in contact with the track? solution
A: N W a y Fy = N + W = m a Loop the Loop
What is the minimum speed such that the ball still stays in contact with the track? Ball falls if N = 0 The corresponding minimum speed is:
A: v2 a= R N =0 v = gR Fy = N + W = ma Car going over bump
How fast must the car go to become airborne? Rounding a curve
A 1500 kg car is traveling on a flat road that passes through a curve with 35m radius. Assuming the coefficient of static friction is 0.5, what is the maximum speed the car can have to stay on the road without sliding? solution
Only centripetal force available is friction force, so the maximal speed is given by:
N arad fs
Fx = f s = marad v2 arad = R f s = s N Fy = N N = mg v max = sgR
v max = 0.5 9.81m /s2 35m = 13m /s W mg = 0 Banked curve
Avoid relying on friction to round a curve: build curve banked at angle : Banked curve
Avoid relying on friction to round a curve. Build curve banked at angle : FBD: W Calculate the angle you need to round the curve at 25m/s! solution
Fx = N sin = marad v2 arad = R Fy = N cos N = mg /cos v2 tan = gR (25m /s) 2 = 60deg = arctan 2 9.81m /s 35m mg = 0 Summary
Dynamics with curved motion
aT=v2/R ap=dv/dt Bumps and loops
Leave surface: N=0 ...
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This note was uploaded on 03/27/2008 for the course PHYS 1112 taught by Professor Leclair,a during the Spring '07 term at Cornell.
 Spring '07
 LECLAIR,A
 mechanics

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