There are two balls touching each other circumferencically. The radius of the big ball is 4 times the diameter of the small all. The outer small ball rotates in anticlockwise direction circumferencically over the bigger one at the rate of 16 rev/sec. The bigger wheel also rotates anticlockwise at N rev/sec. What is 'N' for the horizontal line from the centre of small wheel always is horizontal

SivaSaravanan.K

• Mar 30th, 2006

 

Ans N=64

Rajiv

• Apr 5th, 2006

 

Hi,

Can you specify how did you get this N=64.

dugu

• Apr 7th, 2006

 

Hi

plz can u tell the procedure how u got N=64.

amit k

• Jun 10th, 2006

 

 i think N should be 2.

For the line joining center to be horizontal ,

both balls surface should rotate at same speed.

Circumference of small ball= pie*d

-----=--------   bigger ball= 8 *pie*d

so if you calculate if small ball is moving at 16 rpm

to keep surface horizotal big ball should be moving at 16/8= 2 rpm.

Jone

• Sep 15th, 2011

 

Revoultion o f small ball=16

2*22/7*r=16

r=8/(22/7)

radius of big ball=4d

=32/(22/7)

2*(22/7)R=N

R=32/(22/7)

N=2*(22/7)*32/(22/7)

N=64rev/sec

shraisy

 Profile Answers by shraisy 

• Sep 25th, 2011

 

@Jone : Can you please clearify

small ball takes 16 revolutions per second
i.e in one second it moves distance = 16 * (circumference)
i.e 16 * (22/7 d)


then how are you equating circumference and no of revolutions.
2*(22/7*r) = 16 ???
I don't get it !

Neha Jadli

• Dec 10th, 2011

 

I calculated somehow 2 get the answer 2 b 64rps....
for small ball: Speed=dist/time big ball: Speed=Dist/time
16=2*pi*r N= 2*pi*R
but R=4r
So, N=8*pi*r
pi*r=8
Substitute pi*r for N;
N=8*8
=64rps

arindam

• Dec 21st, 2011

 

2*pi*r*16=2*pi*4*r*N
//as both boll will cover same distence..
N=rev of big ball
=>N=16/4=4...ans

Gopal27

 Profile 

• Jan 28th, 2012

 

16*8=128 is ans..

maddy

• Jul 6th, 2012

 

n2/n1=d2/d1
16/N=d2/(2*4*d2)
N=16*8
N=128

nitish

• Aug 21st, 2012

 

i thing its 2rev/sec.
smaller ball has the radius R.
bigger ball has the radius 8R.
if smaller ball travel distance=16R(as it makes 16 rev per sec),the bigger one has to make(8R+8R=16R).

therefore,the bigger one has to travel twice its own radius,so the answer is 2 rev/sec.

Sasanala

• Sep 7th, 2014

 

Its 2rev/sec dude.. not 64rev/sec.. use common sense.. If the small one rotates at the rate = 16rpm then larger one will rotate with rate less than 16rpm..

Here distance travelled by smaller one in one rotation = 2*pi*r= 2(pi)(r)

Since radius of bigger one = 4times diameter of small one= 4(2r) = 8r;

Here distance traveled by larger one in one rotation = 2*pi*(8r)= (8)[2(pi)(r)]

that is by the time when larger on takes one rotation the smaller one rotates by 8 times..
1 rotation of big -----> 8 rotations of small
? rotation of big-----> 16 rotations of small
? = 2;
so for 2 rotations of big ball you get 16 rotations of smaller one..
Hence if small one has 16rev/sec big one will has 2 rev/sec.

Hope you got it :)