Experiment - A force plate was used to collect the ground reaction forces during a maximum vertical jump and landing

Experiment - A force plate was used to collect the ground reaction forces during a maximum vertical jump and landing. Calculate jump height and compare the difference between the Static Jump and a Counter-movement Jump.

Task 1 -the subject stood on the force plate and performed a maximum vertical jump, starting from a static squat position with hands-on hip at the commencement of the jump the legs do not go lower than the original posture. This is a static jump.

Task 2 - the subject stood on the force plate and performed a maximum vertical jump, with a counter-movement, still with hands-on hip. This is a counter-movement jump

Notes on Data Collection

• Force plate data were collected at 100 Hz

• With the subject standing on the force plate the force was equal to their body weight.

• When the subject was in flight the force plate registered zero.

Useful Concepts

• From the force record you can measure the time in flight

• Jump height can be estimated from half of the flight time:

Jump Height (in meters) = ½g (t/2)2

Where g (gravity) = 9.81 m/s2 and t = time in air

1. On the graphs on the following page mark on each of these graphs the following (10 points)

• bodyweight line. time of initiation of movement counter-movement (only present in one of the jumps)

• instant of take-off

• instant of landing

2. What was the time in flight? (5 points)

3. Given flight time compute the height the subject jumped (20 points, 10 points for each jump)

4. Which jump was higher? Static or counter-movement.

Bonus - Estimate the subjects body weight, and therefore body mass (Assume g = 9.81 m.s) 5 points