# Homework Help: Solving for acceleration

1. Sep 21, 2009

### tjohn101

1. The problem statement, all variables and given/known data

A car at the Indianapolis-500 accelerates uniformly from the pit area, going from rest to 285 km/h in a semicircular arc with a radius of 194 m.

Determine the tangential acceleration of the car when it is halfway through the turn, assuming constant tangential acceleration.
m/s2

Determine the radial acceleration of the car at this time.
m/s2

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?

2. Relevant equations

Unknown

3. The attempt at a solution

Have not attempted yet because I don't know how to start.

2. Sep 21, 2009

### rl.bhat

Without knowing relevant equations you cannot solve the problems.
If you are studying physics, you must have a text book. If you don't have, search in Hyper Physics site. And go through the circular motion. Show your attempts.We will help you if you have made any mistakes.

3. Sep 21, 2009

### tjohn101

The book gives me these, but I don't have enough information to use them nor do I know how to get that information.

Atan= [delta]V/[delta]t

and

Ar=v^2/r

I've tried them to death, but with no good answer. I don't know how to get time, so I don't know how to get acceleration.

4. Sep 21, 2009

### rl.bhat

If there is no tangential acceleration, v^2/r must be equal to g.
Find v1.
Actual velocity v2 is 285 km/h. Convert it into m/s.
v = v2 - v1 is the velocity gained by the tangential acceleration.
Using the formula v = rω,find the angular velocity ω.
Using the initial angular velocity zero, and final angular velocity ω and angular displacement π/2, find the angular acceleration α.
Using the relation a = r*αnd the tangential acceleration a.

5. Sep 21, 2009

### tjohn101

Okay. Could you help me find the answer? I've been cracking at this one for three days. Homework is due tonight, so if you could help me as much as possible that would be great. I'm working on another problem right now

6. Sep 21, 2009

### rl.bhat

I have given some hints. Workout them first. If you stuck up I will help you.