# Solids Elasticity (Bulk Modulus)

## Homework Statement

When the water freezes it expands by about 9.00%. What pressure increase would occur inside your automobile engine block if the water in it froze?(The bulk modulus of ice is 2.00 x 10^9 N/m^2).

## Homework Equations

$$B=\frac{\Delta P}{\Delta V / V_i}$$

## The Attempt at a Solution

If I solve the problem "forward in time" I get this:
$$\Delta P=\frac{1.09V_i-Vi}{Vi}B=0.09B$$

but if solving the problem "backwards in time"

$$\Delta P = \frac{V_i-1.09V_i}{1.09V_i}B = 0.0826B$$

Shouldn't both answers have the same magnitude?

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