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January 29, 2015

January 29, 2015

Posted by **Morgan** on Tuesday, March 23, 2010 at 4:02pm.

An automobile engine slows down from 4500 rpm to 1500 rpm in 2.5 seconds.

a) calculate angular accceleration

b)calculate total number of revolutions done in this time.

What I did:

a) I got the answer, and it was right, and it was also negative, but: what confused me was b

b) It is decelerating, this really confused me. I wasn't even sure how to approach this.

- physics -
**bobpursley**, Tuesday, March 23, 2010 at 4:37pmaverage speed=4500+1500 divided by 2, or

average speed=3000 rpm

displacement=avgspeed*time

=3000rpm or 3000rev/3600sec *2.5sec

= 7500/3600 rev

- physics -
**Morgan**, Tuesday, March 23, 2010 at 11:02pmI'm sorry, I tried this and got 2.1 and the computer keeps kicking it out as wrong. Your logic makes sense to me after I thought about it. Is there something I'm doing wrong?

- physics -
**Morgan**, Tuesday, March 23, 2010 at 11:09pmwait never mind. There are only 60 seconds in a minute!

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