# Helps needed with this diff qn!

1. Jul 11, 2009

### miraclezdr

a material decays at a rate proportional to its mass. there are 200mg of it initially, 5 hours later, it lost 10% of the original mass. let m denote the mass of remaining at anytime t. write the differential equation which describes the rate of change of m with respect to t, and solve the equation.

Last edited by a moderator: Jul 11, 2009
2. Jul 11, 2009

### Hootenanny

Staff Emeritus
Welcome to Physics Forums.

What have you tried thus far?

3. Jul 11, 2009

### Feldoh

a material decays at a rate proportional to its mass. -> Is giving you the basic differential equation.

there are 200mg of it initially, 5 hours later, it lost 10% of the original mass. -> Tells you how they are proportional.

You've just got to learn how to read the problems^^