not bad

One end of a spring of unstretched length L and force constant k
is fixed to a pivot, and a body of mass m is attached to its other end
The spring is released from an unstretched, horizontal position, as
shown in figure

What is the length of the spring when it reaches a vertical position?

8 Answers

1
ith_power ·

use energy conservation.

mg(x+L)=1/2 m v^2 + 1/2 k x^2 + 1/2 m(x+L)^2 w^2

from free body diagram
mg+m v^2/(x+L)= k x.
we have to solve them to get x

1
Rohan Ghosh ·

ur first equation doesnt seem to be correct

1357
Manish Shankar ·

yes i wud agree priyam..

basically power.. u are probably repeating energy terms !

1
ith_power ·

is there any term missing???

62
Lokesh Verma ·

you need to define w clearly and v clearly..

what is the direction of v..

and about which point is this w.

1
Rohan Ghosh ·

1/2 mv2
is the same as
1/2m(x+l)2w2

youve repeated it

1
ith_power ·

yeah you are right, if mass of spring were given then rotational KE would come or else itwouldn't.

so it should be mg(x+L)=1/2 m v^2 + 1/2 k x^2

62
Lokesh Verma ·

Good work guys.. i will try to post the final solution.. I should have last nite.. but din get time to..

use energy conservation.
mg(x+L)=1/2 mv2 + 1/2 k x2

from free body diagram
mv2/(x+L)= kx - mg

And now again i feel like .. eeks who will!!!

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