Berkeley Review Physics 1 Book Page 25

[pandolinus]

So I started the sn2ed schedule, going fine so far, but I stumbled upon this possible mistake.

On page 25 Berkeley Review Physics 1:
We can demonstrate the use of equation (1.18) by timing a falling steel ball. In
Figure 1-10 we have a measuring stick with a magnet at the top. The steel ball is
attached to the magnet. At a distance of roughly 0.3 m below the magnet is a
light beam; at a distance of roughly 1.2 m below the magnet is another light
beam. Releasing the steel ball from the magnet starts the timer. The times at
which the light from the first light beam and second light beam are interrupted
by the falling steel ball are recorded.



From this experiment, it is possible to
calculate the time it takes the steel ball to reach the first and second light beams.
The answer that we should get is 0.25 seconds for the first beam and 0.50seconds
for the second beam. The solution to this demonstration is shown below:

How did the book arrive to .25 seconds for the first beam if the distance is only 0.3 m?
the calculation they provide states 1 m for the first beam but it clearly stats .3m ?

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[desperadoflakes]

It's essentially just saying that the ball will fall 0.3m in 0.25 seconds, and 1.2m in .5 seconds. This makes sense:

h = 1/2gt^2 = 5 * (.25)^2= 5*.0625= .31m

h = 1/2gt^2 = 5*(.5)^2 = 5*.025 = .125m