68 - Rotational mechanics Questions Answers
IN THE PREVIOUS QUES ( THAT WAS FROM ROTATn TOPIC , SUBMITTED 5 DAYS AGO) , I AM STILL NOT GETTING THE SOLn SUBMITTED BY YOU.
if this is the question based on number of rotations then read it carefully
a coin placed on a gramophone record rotating at 33rpm flies off d record , if it is placed at a dist. of more than 16cmfrom d axis of rotation . If d record is revolving at 66rpm , the coin will fly off if it is placed a distance not less than ?
ans=4cm
coin will fly off, if it will gain the required centrifugal
so apply mrω2 = mRW2
FROM REST A BODY ROTATE 120 rotation/min FOR 20 sec THEN IT ROTATE FOR 5sec WITH SAME ROTATION . FIND HOW MANY ROTATn IT WILL MAKE?
ω = ω0+ αt
so 4π = 0 + α20 so α = π/5
so total angular displacement = 1/2 π/5 202 = 40 π = 20 rotation
and with angular velocity 2 rotation/sec total rotations in 5 sec. = 10
so answer will be 20+10 = 30
IN THAT QUES OF CENTRE OF MASS BOTH THE OPTION ARE GIVEN THEN IN EXAM HOW WE KNOW THAT WHICH ONE IS CORRECT. AS WE USE Vm /M+m =V OF PLANK & m= mass of man
I could not understand, what the question is,
A SYSTEM OF m1 &m2 THE PARTICLE m1 IS PUSHED TOWARDS THE CM OF PARTICLES THRU DIST. d BY WHAT DIST. WOULD m2 MOVE SO AS TO KEEP MASS CENTRE OF PARTICLES AT THE ORIGINAL POSITION
SIR, I WANT TO KNOW Y ans is m1d/m2 WHY NOT m1d/ m1+m2?
with centre of mass as reference point m1d = m2x so x can be calculated.
sir, can u please post a topic on rigid body rotation ? mainly heip to solve question please. with some examples.
Yes, I will do very soon.
Why earth moves in orbital motion around the sun ...? why not in circular motion...?
Since every heavenly body like sun, earth, moon are rotating freely in free space, there is no body which is placed on a base, so rotation of every body depends on all the surrounding bodies. It means its track will also depend on the attraction forces given by all the surrounding bodies.
Two cylinders are twisted by the same external torque.If the ratios of their modulous of rigidity , radii & lengths are 1:2, 2:3 & 3:4 respectively. Then find the ratio of angle of twist ??
Let the angle rotated due to torque = θ and angle of twist (shear) = δ
then arc covered = rθ (here r is radius)
now for twist of wire δ = rθ/l (here l is length)
according to formula η = F/Aδ and torque ζ = kFr (here k is constant of proportion)
we get ζ = kηAδr
Use the formula and get the answer, you have to calculate ratio of δ's so k is not required