# Energy Problem Involving Spring Force

1. Apr 7, 2009

### angotta

1. As a 1.7×104 jet plane lands on an aircraft carrier, its tail hook snags a cable to slow it down. The cable is attached to a spring with spring constant 6.0×104 . If the spring stretches 31 to stop the plane, what was the plane's landing speed? (Answer in m/s)

2. Relevant equations
Fsp=k$$\Delta$$s where k is the spring constant and $$\Delta$$s is the change in position.
Also possibly the Equation for kinetic energy
K=1/2mv2
And also posibly
vf2=v i2+2a$$\Delta$$s
where v is velocity and a is acceleration

Also the conservation of energy and momentum equations are possible along with f=ma

3. The attempt at a solution

I found the spring force to be 1860000 N and then I lost where to go exactly. I tried to use F=ma to find acceleration, and then use kinematics (vf2=v i2+2a$$\Delta$$s) because v final should be zero, but I got the wrong answer. My incorrect answer was 82m/s.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Apr 7, 2009

### LowlyPion

Maybe consider using the KE and PE of spring?

1/2*m*v2 = 1/2*k*x2

v2 = k*x2/m = 60,000*312/17,000