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Sharks Goalie Wade Flaherty is just outside the crease after clearing the
puck down the ice.
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Just how fast is a goalie's reaction time?
Let's see what reaction time is required of Sharks Goalie
Kelly Hrudey when an opposing player launches a speedy slapshot towards
the net. If the opposing player has time to tee up and get solid wood on
the puck, Hrudey could easily be facing a shot of up to 90 mph. The reaction
time of the goalie can be calculated using the equation
Describing motion is a part of mechanics known as
kinematics
.
Physicists call this a kinematic equation.
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If someone shoots from the blue line, a rather generous
distance of 60 feet, the time it takes for the puck to travel to the net
is
To translate 90 mph into feet per second (5280 feet =1 mile/
3600 seconds =1 hour), then
90 x 5280 = 475, 200 feet per hour.
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475, 200
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= 132 feet per second = 90 mph
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3600
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60 feet
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= .456 seconds
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132 feet per second
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This doesn't allow very much time for the goalie to move
himself and all that equipment over to save the puck. Try testing your own
reaction time, for a better understanding of what a goalie has to do.
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How fast are you?
(modified from
the book
The Sporting
Life
)
You can measure your reaction time with just a yardstick
and some help from a friend. Rest your arm on the edge of a table or chair,
with your hand hanging over the edge (this prevents you from dropping your
hand down to match the yardstick's motion). Hold your thumb and index finger
about an inch apart, and have a friend hold a yardstick so that its bottom
end is just between your two fingers. Without warning you, have your friend
drop the yardstick and, as fast as you can, close your fingers on the stick.
Note the inch reading where your fingers hold the stick. For most people,
about six inches will have fallen through before they can grab the yardstick.
If you want to convert the distance the yardstick fell
to a reaction time, use the following table:
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Inches Fallen
|
ReactionTime in Seconds
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5.0
|
0.161
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5.5
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0.169
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6.0
|
0.177
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6.5
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0.184
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7.0
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0.191
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7.5
|
0.198
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8.0
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0.204
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8.5
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0.210
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This grab at 7 inches is good enough for a web developer but wouldn't cut
it for a goalie.
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Thinking of going pro?
The average person usually catches the yardstick around 6-8 inches; this
translates to a reaction time of .177 to .204 seconds. Thinking of going
pro? Wait until you consider this next situation.
If the opposing player uses the room between him and the
net to his advantage and skates up so that he tees up at a distance of twenty
feet from Hrudey, he will effectively minimize the time that Hrudey has
to deflect the puck out of the way. If the puck is traveling at 100 mph
at the time it reaches Hrudey, let's see how quick he has to be:
Time = d/t = 20 ft/90 mph = 0.152 sec.
For a reaction time like that, Hrudey would have to catch
the yardstick at 4.5 inches. Maybe you'd better keep your day job.
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Click the "forward"
button below to continue.
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©
Exploratorium
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