1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: A homework assignment including rotation of a rigid body

  1. Mar 14, 2015 #1
    1. The problem statement, all variables and given/known data
    The problem is this: A car is evenly slowing down from 30 km/h to 0 in the time of 2 seconds. Radius of its wheels is 30 cm. What is its angular acceleration and what total angle will the wheel describe until it stops? How many turns does the wheel make and what is the length of the path the car travels while stopping?

    2. Relevant equations
    [tex]\alpha = \frac{\Delta \omega}{\Delta t} [/tex][tex]\omega = \frac{\phi}{t} [/tex][tex]\phi= \frac{\alpha}{2}t^2 [/tex][tex]s = vt [/tex]

    3. The attempt at a solution
    I honestly tried to use moment of inertia and tangential force equations and I just can't figure it out, every time I find a matching equation, something is missing and I can't solve it. Please help me, at least by some tips if you don't wanna do the whole problem. Thanks.
  2. jcsd
  3. Mar 14, 2015 #2

    Quantum Defect

    User Avatar
    Homework Helper
    Gold Member

    You are over-thinking this. Think about how you can change the linear speed into a rotational velocity of the wheel. Hint: Today is appropriately 3/14/15, using the us convention for the date! From the initial angular velocity and the time to stop, you can calculate alpha, and on you go.
  4. Mar 15, 2015 #3
    Thank you, I'll try it and report back!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted