- #1

DracoMalfoy

- 88

- 4

## Homework Statement

A toy gun is pointed toward the sky. A Styrofoam ball of mass 10g is at rest against a spring compressed 2cm. The spring is released causing the ball to move upward through the air to a max height of 1m. The air exerts a frictional force of 0.35N on the ball. What is the spring constant(k) of the spring? (Answer: 2240N/m)

## Homework Equations

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.5m⋅Vi^2+.5Kxi^2+mg⋅yi+Ff⋅Δd=.5m⋅Vf^2+.5Kxf^2+mg⋅yf

## The Attempt at a Solution

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I revised the equation as:

.5⋅Kx^2+Ff⋅Δd=mg⋅yf

I took out velocity since it isn't offered in the problem.

m=10g=.01kg

x=2cm=.02m

Δd=1m

Ff=0.35N

K=?

I converted g to kg and cm to m. Then I tried to solve for k.

.5⋅K(.02)^2-.35⋅1=.01⋅9.8⋅1

.0002K-.35=0.98

.0002K=.63

K=.63/.0002

K= 3150

So... I don't know exactly what I did wrong here. I thought that I was on the right path.