OCR MEI Paper 2 Specimen — Question 14

Exam BoardOCR MEI
ModulePaper 2 (Paper 2)
SessionSpecimen
TopicFirst order differential equations (integrating factor)

14 In a chemical reaction, the mass \(m\) grams of a chemical at time \(t\) minutes is modelled by the differential equation
\(\frac { \mathrm { d } m } { \mathrm {~d} t } = \frac { m } { t ( 1 + 2 t ) }\).
At time 1 minute, the mass of the chemical is 1 gram.
  1. Solve the differential equation to show that \(m = \frac { 3 t } { ( 1 + 2 t ) }\).
  2. Hence
    1. find the time when the mass is 1.25 grams,
    2. show what happens to the mass of the chemical as \(t\) becomes large.