How to Calculate Net Impulse from Jumping Motion Analysis

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To calculate the net impulse from a jump, the initial momentum (p) is determined by multiplying the mass (80.6 kg) by the take-off velocity (5.3 m/s), resulting in 427.18 kg·m/s. The impulse (I) is then calculated using the formula I = F * t, where F is the average force and t is the contact time (0.25 s). However, the second calculation presented (427.18 * 0.25 = 106.8) is incorrect, as it misapplies the impulse formula. The correct approach requires understanding that impulse equals the change in momentum, not a direct multiplication of momentum by time. Clarification on the calculations is necessary to ensure accurate understanding of impulse in this context.
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Homework Statement


A person with a mass of 80.6 kg jumps from a squat position into the air. The velocity
at the beginning of the jump is zero. Fast motion video analysis reveals that the
velocity of the centre of mass at take-off was 5.3 ms-1. Foot contact time when the
ground reaction forces are being generated is 0.25 s. What is the net impulse?


Homework Equations



I = change in p
p = m * v
I = F * t

The Attempt at a Solution



80.6 * 5.3 = 427.18
427.18 * 0.25 = 106.8

Can someone please check this, I think I've made a mistake

Thanks heaps =)
 
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Trandall said:
I = change in p
This is all you need.

80.6 * 5.3 = 427.18
427.18 * 0.25 = 106.8
Why don't you describe what you were doing in each of these calculations? (One makes sense, the other doesn't. :wink:)
 

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