A spring of negligible mass having a force constant of `10Nm^(-1)` is compressed by a force to a distance of 4 cm. A block of mass 900g is free to leave the top of the spring. If the spring is released, the speed of the block is

Options

A. `11.3ms^(-1)`
B. `13.3xx10ms^(-1)`
C. `13.3xx10^(-2)ms^(-1)`
D. `13.3xx10^(-3)ms^(-1)`

Answer

C

Explanation

`"We know that the potential energy of the spring"=1/2kx^(2)`. Here the potential energy of the spring is converted into kinetic energy of the block.
`1/2kx^(2)=1/2mv^(2)`
`v^(2)=k/mx^(2)impliesv=sqrt(k/m)x`
`v=sqrt((20)/(90))xx4xx10^(-2)=sqrt((100)/9)xx4xx10^(-2)=13.3xx10^(-2)ms^(-1)`