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Topic Date User

measuring dissipation of force of bouldering mats 12-May-2006 At 9:10:26 PM G

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From a theoretical perspective the force on the boulderer could be estimated from their rate of change in momentum (a rearrangement of the impulse equation which can be derived from F=ma).

Force = (mv2 (momentum at point 2) - mv1 (momentum at point 1))/time
Tthe longer the time it takes to reduce the boulderer's momentum to zero (i.e. come to a stop) the less force - think a very soft spongy mat that you sink into without bottoming out compared to a hard pile of closed cell foam.

In terms of numbers:
mv2 = 0 because it is after they have landed and the mat is compressed.
mv1 could be just before they hit the mat. From a theoretical point of view it would be easier to model the climber as a solid ball to remove the complication of legs absorbing any impact. Assume m=75kg (my mass), and v = 4 m/s (I fall from about 1 m and land flat on my arse - the 4 comes from v^2=u^2-2as). So mv1=300
time I will assume is 0.2 seconds. I guestimate this based on the fact that landing on my arse seems to be over fairly quickly.

Therefore Force = (0 - 300)/0.2 = 1500 N which is a force equivalent to sitting a 150 kg weight on top of me.

In terms of measuring the force you could either:
1. place the bouldering mat on top of some sort of load cell which measures force, then have someone fall on it.
2. measure someones velocity just before they hit the mat and measure the time it takes from when they hit the mat until they come to a stop, then use the equation above.

Hope this helps