x=...............

A uniform rod of length l is pivoted at pt. A.It is struck by horz. force which delivers an impulse J at distance x from pivot.For what value of x , the impulse delivered by pivot is equal to zero??????????

6 Answers

62
Lokesh Verma ·

Hint: The impulse will be zero at the point where the instantaneous velocity is zero..

Just try to solve.. if u cant .. do let me know!

24
eureka123 ·

i have been trying it for 2 days.....................i didnt get the answer,thats why i posted it here..................

33
Abhishek Priyam ·

Eureka!!! I got it :P

See if pivot impulse is zero then ang momentum about the point of application of impulse will be conserved.. and also about the pivot Jx=ml2/3ω.......... waise no need of this :P

also as pivot is axis of rotation therefore vc=ωl/2

about point of application of J

mvc(x-l/2)-ml2/12ω=0
where vc=ωl/2

therefore mωl/2(x-l/2)=ml2/12ω
(x-l/2)=l/6

x=l/6+l/2...
x=2l/3...

Note it doesn't depend on J...

also if there have been any collision then it doesn't depends on coefficient of restitution and velocity or mass of colliding particle and not on mass of rod also..

It only depends on length of rod :P

33
Abhishek Priyam ·

Pink so fast :)

Good speed... :>

33
Abhishek Priyam ·

I was thinking of putting this question on forum for others.. but Eureka did it... :)

23
qwerty ·

angular impulse abt axis of rotation can also be taken right ?

linear impulse

J = mv_{com}= \frac{m\omega L}{2} ..........(1)

angular impulse

Jx=\frac{mL^{2}\omega }{3}.............(2)
divide 2 by 1

x = \frac{2L}{3}

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