# Homework Help: Work help i'm stuck and about to kill myself

1. Dec 5, 2005

### howru

work help!!!!!!!! i'm stuck and about to kill myself

A car at the Indianapolis-500 accelerates uniformly from the pit area, going from rest to 320 km/h in a semicircular arc with a radius of 192 m.

Determine the tangential acceleration of the car when it is halfway through the turn, assuming constant acceleration.
m/s^2(tangent to the path)
(I know that the equation is equal to mv2/r but how do i set it up. what is the difference between tangent and toward the center.)

Determine the radial acceleration at this time.
m/s^2 (toward the center of the path)
(It is rev/sec and multiply. i got 3.7m/s^2)

If the curve were flat, what would the coefficient of static friction have to be between the tires and the roadbed to provide this acceleration with no slipping or skidding?

(mu=fN I got all these other formulas and forces on the car and put them together, and i got .48 but it's wrong)

2. Dec 5, 2005

### Astronuc

Staff Emeritus
This might help.
http://hyperphysics.phy-astr.gsu.edu/hbase/rotq.html, specifically http://hyperphysics.phy-astr.gsu.edu/hbase/rotq.html#req

and this is a nice reference

http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html#rlin

The tangential velocity is the linear velocity tangent (parallel) to the trajectory, which is perpendicular to the radial direction for a semi-circle.

The key here is that the acceleration is uniform. The car starts with 0 velocity and reaches 320 km/h at the end of the semi-circle of radius 192 m, and it must travel a distance x = $\pi$*192 m. Note that the angle through which the acceleration takes place is $\pi$ radians.

Last edited by a moderator: Apr 21, 2017