Question

A bacterium moves with a speed of 3.5  across a petri dish with a radius of 8.4 cm. How long does it take the bacterium to traverse the petri dish? (Hint: assume it travels through the centre of the dish.)

Answer 1

The total distance the bacterium has to travell is $d = 2\cdot 8.4cm = 16.8cm$ (the diameter of the dish). I assume that the speed of the bacterium is $v = 3.5cm/min$. Then the time it takes the bacterium to traverse the petri dish is:

$$t = \dfrac{d}{v} = \dfrac{16.8cm}{3.5cm/min} = 4.8min$$

Answer. 4.8 minutes.