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A block of mass 'm' is attached to a spring of constant k= 4mg/L and

natural length 10L. The system is released from rest, L above the ground.

Q)
Till the block reaches its lowest position for the first time, the time duration for which the spring remain compressed is- ?

12 Answers

1
Unicorn--- Extinct!! ·

Q2)

A tank contains a liquid of density ρ.

A cylinder of density ρ/4 and length L is is kept in equilibrium position by means of an external force, vertically downwards.

The cylinder is just submerged. AT t=0, the external force is removed instantaneously. Assume the liquid level remains same.

The speed of cylinder when it reaches equilibrium position is- ?

Edit: Area of cylinder is 'a' and that of tank is 'A' (a<

1
Unicorn--- Extinct!! ·

These are basics, guys.. need your help.

49
Subhomoy Bakshi ·

instantaneously means how much time??? I was stuck in a HCV prob due to this instantaneous word!![2][2]

49
Subhomoy Bakshi ·

F=-kx

a=-kx/m=-(4g/L)x

so, a=\frac{dv}{dt}=\frac{dv\: dx}{dx\: dt}=v\frac{dv}{dx}=-\frac{4g}{l}x

\Rightarrow \int_{v_{o}}^{v}{(v)}\:{dv}\;=\;\int_{x_o}^{x} (-\;\frac{4g}{l}x)\: dx

v^{2}-v_o^2=-\frac{4g}{l}(x^2-x_o^2)

which boils down to,

v^{2}=-\frac{4g}{l}x^2+C\;\;\;\;[where\;C=const=v_o^2+\frac{4g}{l}x_o^2]

(\frac{dx}{dt})^{2}=-\frac{4g}{l}x^2+C

this can be used to find the relation between x and t using techniques of integration...[1][1]

49
Subhomoy Bakshi ·

vo has to be found out using equations of motion and xo is 10L

final x ie maximum compression will be found out using conservation of energy...
initial kinetic energy+loss in potential energy=compression in spring...[1][1]

1
Unicorn--- Extinct!! ·

instantaneously means there is no time lag...

1
Unicorn--- Extinct!! ·

Thanx subho..can u post the answer to the above question?

I just want to match the answer. [1]

49
Subhomoy Bakshi ·

does that mean that instantaneously removing force equals at the time T=0 the force is removed and never it is applied back!!

1
Unicorn--- Extinct!! ·

It means that at 't'=0 there is a force acting on the system..and at 't'= t+Δt the force is not acting.

Δt→0

1
Unicorn--- Extinct!! ·

Also, the force is never applied back.

49
Subhomoy Bakshi ·

ok clear thank you!!!

i cnt access instant chat....so wait i ll have to reconnecct modem...net giving problems...:(:(:(

1
Unicorn--- Extinct!! ·

No problem.

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