|
Now that you know about the three types of sprint starts, you're probably wondering, "Which one is the best?" We
will now show and explain to you which one is the most effective in giving you the best possible time.
We made an experiment to test the different sprint starts so that you can learn about the types of starts and figure out
which one is the best on your own. If you chose to complete the experiment, you can check with our results later.
First of all, you have to know what you are trying to achieve when deciding which start is the most effective. The purpose
of the start is to give you the best possible acceleration out of the starting position as well as giving you the best velocity
and reaction time out of the blocks.
Now, here is our experiment which we devised to find which start is the most effective in giving you the best velocity.
In order to have a good velocity, you need to have a good IMPULSE off of the blocks. Impulse is the force acting over a period
of time. In this case, it would be the force your feet pushes against the block over the time at the beginning of the race
to allow you to accelerate to the fastest initial velocity.
SPRINT START EXPERIMENT
PURPOSE:
To study the three different crouched starts and to determine which is the most effective in achieving the greatest impulse
giving the sprinter the best velocity out of the starting position.
MATERIALS:
-stopwatch
-measuring tape
-running track
THEORY:
We have to use two different formulae in this experiment. Here is an explanation of them.
v=d/t
This is the formula for velocity. Velocity is the same as speed. The only difference is that velocity has direction, where
speed doesn't. Velocity is the quotient of the sprinters displacement (distance covered) and the time it takes to travel this
distance.
(F)(t)=(m)(v)f-(m)(v)i
This is the impulse momentum formula. You're probably wondering what its all about, but when its broken down it can be
very simple.
first of all:
Impulse is equal to the force acted over time (as already mentioned). It is shown like this:
impulse=(F)(t)
Since we can not determine the force very easily, we are going to use another approach. Impulse is also equal to the chage
in MOMENTUM. Momentum is the product of the object's. or in this case the sprinter's, mass and velocity. Momentum is used
a lot everyday in describing different things, such as saying "The player is gathering momentum as he moves down the
ice" or "The cars momentum carried it off the road." Momentum is difficult to explain but hopefully you'll
get the general idea.
Because it is easier to determine the runner's mass and velocity, we will be using this formula, the change in momentum,
to determine impulse.
PROCEDURE
1)First of all, find a smooth flat running surface.
2)Then measure out a distance of 10 m from the starting line.
3)Then have the runner get into the bunched start at the starting line. The buched, or bullet start, is the start which
your front foot and back foot are closest together in the starting position.(there are pictures at the bottom to give a visual
explanation)
4)Then have another person at the finish line (10 metres away) to time the runner's first portion of the race.
5)Then have the runner in the bunched start practice sprinting to the 10 metre line at least three times to insure that
they are able to perform it.
6)Then time the person, using this start, three times.
7)Then move on to the medium start. This is the start where your feet aren't close together, but they aren't far apart
either. The toe to toe distance is opproxomately 40-55cm's.
(there are pictures of this at the bottom)
8)Have this one practiced then record the times of three trials.
9)Then repeat the same experiment for the elongated start. The elongated start is the one in which your back foot is furthest
behind the front one.
10)After the times for the nine trials have all been recorded, find the average time it takes to run the 10 metres for
each start. (It is easiest to record this information in a chart, we have one you can copy in the results section)
11)Then determine what the velocity was for each of the starts using the velocity formuala: v=d/t
Fill in the distance(10 metres) and the average times for each start to determine the velocity.
12)After, determining the velocity for each start, you can determine the change in momentum. To do this, have to find
the momentum before and after. You also must find the mass (in kilograms) of the person running.
To find the initial and final momentum, fill in the velocity and mass for each of the starts into the following formula.
(m)(v)f-(m)(v)i= change in momentum
m=mass v=velocity f=final i=initial
13)Once the change in momentum for each of the sprint starts is calculated, you have the impulse. (this is because the
change in momentum is equal to the momentum)
14)Then determine which start gives the greatest impulse. Then you will know which start allows for the greatest force
over time resulting in the best velocity out of the blocks.
RESULTS
For our experiment, we tested three different people so that our results would be more accurate.
Speed of Person #1 (mass=42 kg) for 10 m
 |
|
|
Type of Start
|
Trial 1
|
Trial 2
|
Trial 3
|
Average
|
|
BULLET
|
3.00 s
|
3.1 s
|
2.77 s
|
2.96 s
|
|
MEDIUM
|
2.71 s
|
2.42 s
|
2.64 s
|
2.59 s
|
|
ElONGATED
|
3.05 s
|
2.83 s
|
2.98 s
|
2.95 s
|
|
|
|
Speed of person #2 (mass=57 kg) in 10 m
Speed of person #3 (mass=60kg) in 10 m
Velocity of each runner in 10 m
Momentum of each person in each start for 10 m
|
