Centripetal acceleration fan problem

AI Thread Summary
A ceiling fan rotates at 100 revolutions per minute, and a spider on its blade risks losing grip if centripetal acceleration exceeds 0.3g. Calculations show that the time period is 0.6 seconds, leading to an angular velocity of 10.47 rad/s. Using the formula for centripetal acceleration, the distance from the center where the spider can safely cling is calculated to be 2.7 cm. However, there is confusion regarding the correct answer, with some claiming it to be 1.05 m. The discussion highlights discrepancies in textbook solutions, suggesting that the problem may be misrepresented in educational materials.
Adsy
Messages
4
Reaction score
0

Homework Statement


A ceiling fan is turning at a rate of 100 revolutions per minute. A spiders is clinging to a blade of the fan. If the spider experiences a centripetal acceleration greater than 0.3g, it will lose its grip on the blad and be flung off. How far from the centre of the fan can the spider safely go?

Rate = 100 rev/sec

a = 0.3g

r=?

Homework Equations



\omega=\frac{\Delta\theta}{\Delta t}

\omega=\frac{2 \pi}{T}

v= \omega r

T= \frac{2 \pi}{\omega}

a=\frac{v^{2}}{r}

a=\omega^{2}r

The Attempt at a Solution



I've worked out that the time period, T = 0.6s

a=0.3g=2.94 ms^{-2}

then use: \omega=\frac{2 \pi}{T}

\omega=\frac{2 \pi}{0.6} = 10.47 rad s^{-1}

then I rearrange this formula: a=\omega^{2}r

r= \frac{a}{\omega^{2}}

then put in the known values to find r
r= \frac{2.94}{10.47^{2}} = 2.7*10^{-2}m

*fixed*

This is incorrect. What am I doing wrong?
 
Last edited:
Physics news on Phys.org
Adsy said:
then put in the known values to find r
r= \frac{2.94}{10.47^{2}} = 2.7*10^{2}m

This is incorrect. What am I doing wrong?

2.7*10^{-2}m = 27mm
 
Oh, that's just a mistake with TeX.
That answer is still incorrect.

The correct answer is 1.05m but how do you work it out?
 
I think there's a mistake in your "correct" solution.
The solution is 27mm.
The problem is rather simple.
Other readers may double check the result.
 
I've asked my friend about this question. He also said the answer is 2.7cm.
Hmm... maybe my textbook has an incorrect solution...
 
Yep. My answer is correct. I've Googled the problem and found other people struggling with the same question. The book is incorrect. Silly Edexcel...
Thanks anyways, Quinzio!
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Trying to understand the logic behind adding vectors with an angle between them'
My initial calculation was to subtract V1 from V2 to show that from the perspective of the second aircraft the first one is -300km/h. So i checked with ChatGPT and it said I cant just subtract them because I have an angle between them. So I dont understand the reasoning of it. Like why should a velocity be dependent on an angle? I was thinking about how it would look like if the planes where parallel to each other, and then how it look like if one is turning away and I dont see it. Since...
Back
Top