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# As shown on next slide, 180cm and 75kg wide receiver cached the ball, lost balance and fell on ground as shown below, and had a concussion.

1.

As shown on next slide, 180cm and 75kg wide receiver cached the ball, lost balance and fell on ground as shown below, and had a concussion. Assume that pivot point of body rotation during the fall is his left foot and took 0.2 sec.

Using reasonable anatomical and engineering assumptions,

Determine, at the moment of impact,

1. The impact speed of head to the ground
2. The force on head

Assume that whole body act as a rigid body during the fall, and center of gravity of whole body is about a inch above belly button.

Hint: First of all, determine the angular velocity of CG of whole body at ground impact.

You may use the table in the link to determine weight of body parts

http://www.exrx.net/Kinesiology/Segments.html

2.

As shown on next slide, 180cm and 75kg wide receiver was running with speed of  15mph forwad, and turned his body 180 degree to cached the ball. After catch, he lost balance and fell on ground as shown below. Assume that his body did not move horizontally during the fall, and pivot point of body rotation during the fall is his left foot and took 0.2 sec.

Using reasonable anatomical and engineering assumptions,

At the moment of impact head on ground, determine the G force on his head.

Assume that whole body act as a rigid body during the fall, and center of gravity of whole body is about a inch above belly button.

Hint: First of all, determine the angular velocity of CG of whole body at ground impact.

You may use the table in the link to determine weight of body parts

http://www.exrx.net/Kinesiology/Segments.html

3.

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As shown on next slide, 180cm and 75kg wide receiver was running with speed of  15mph forward, and turned his body 180 degree to cached the ball. At the time of catch, his body is still moving backward with 15 mph because of momentum. After the catch, he lost balance and fell on ground as shown below.

However, because of flexibility of his neck, at the beginning of rotation, head flexed 45 degree, and maintained the angle until his back hit the ground, then neck started extension, finally hit this head to the ground.

Assume that his body did not move horizontally during the fall, and pivot point of body rotation during the fall is his left foot, and it took 0.2 sec until his back hit the ground and 0.05 sec his head hit the ground after that.

Using reasonable anatomical and engineering assumptions, determine the G force on his head at the moment of head impact on ground,

Assume that whole body act as a rigid body during the fall, and center of gravity of whole body is about a inch above belly button.

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