Answer
(a) The average speed across each synapse is $1.0\times 10^{-3}~m/s$
(b) It takes $20.2~ms$ for the signal to reach the brain.
(c) The average speed is $99.0~m/s$
Work Step by Step
(a) We can find the average speed $v_{ave}$ across each synapse:
$v_{ave} = \frac{d}{t} = \frac{100\times 10^{-9}~m}{1.0\times 10^{-4}~s} = 1.0\times 10^{-3}~m/s$
The average speed across each synapse is $1.0\times 10^{-3}~m/s$
(b) We can find the time $t$ across each sensory neuron:
$t = \frac{d}{v} = \frac{1.0~m}{100~m/s} = 0.010~s = 10.0~ms$
We can find the total time:
$2\times 10.0~ms~+~2\times 0.10~ms = 20.2~ms$
It takes $20.2~ms$ for the signal to reach the brain.
(c) We can find the average speed:
$v_{ave} = \frac{d}{t} = \frac{2.0~m+200\times 10^{-9}~m}{0.0202~s} = 99.0~m/s$
The average speed is $99.0~m/s$
