Physics 11: How to Calculate Spring Compression with an Applied Force of 6.0 N

[roxxyroxx]

Homework Statement

A spring can be compressed 12 cm by an applied force of 6.0 N. A 2.8 kg box sliding along a frictionless surface approaches this spring at a speed of 1.9 m/s. How far will the spring be compressed when the box comes to a stop?

Homework Equations

E_{p = 0.5kx²}

0.5mv² = 0.5kx²

The Attempt at a Solution

I worked out that k = 50 N/m
0.5mv² = 0.5kx²
0= 25x²

but this doesn't work out because x should be 0.45 m. help?

 

[LowlyPion]

When the box comes to a stop all of the Kinetic Energy will be converted to the potential energy of the spring.

Use the formula you had only put the initial KE of the box in before it touches the spring.

And all will be well.

 

[roxxyroxx]

great thanks !