BIO Head injuries in sports A research group at Dartmouth College has developed a Head Impact Telemetry (HIT) System that can be used to collect data about head accelerations during impacts on the playing field. The researchers observed 249,613 impacts from 423 football players at nine colleges and high schools and collected collision data from participants in other sports. The accelerations during most head impacts (>89%) in helmeted sports caused head accelerations less than a magnitude of 400 m/s 2 . However, a total of 11 concussions were diagnosed in players whose impacts caused accelerations between 600 and 1800 m/s 2 , with most of the 11 over 1000 m/s 2 . Suppose the average speed while stopping was 4 m/s (not necessarily the correct value) and the collision lasted 0.01 s. Which answer is closest to the head’s stopping distance (the distance it moves while stopping)? a. 0.04 m b. 0.4 m c. 4 m d. 0.02 m e. 0.004 m
BIO Head injuries in sports A research group at Dartmouth College has developed a Head Impact Telemetry (HIT) System that can be used to collect data about head accelerations during impacts on the playing field. The researchers observed 249,613 impacts from 423 football players at nine colleges and high schools and collected collision data from participants in other sports. The accelerations during most head impacts (>89%) in helmeted sports caused head accelerations less than a magnitude of 400 m/s 2 . However, a total of 11 concussions were diagnosed in players whose impacts caused accelerations between 600 and 1800 m/s 2 , with most of the 11 over 1000 m/s 2 . Suppose the average speed while stopping was 4 m/s (not necessarily the correct value) and the collision lasted 0.01 s. Which answer is closest to the head’s stopping distance (the distance it moves while stopping)? a. 0.04 m b. 0.4 m c. 4 m d. 0.02 m e. 0.004 m
BIO Head injuries in sports A research group at Dartmouth College has developed a Head Impact Telemetry (HIT) System that can be used to collect data about head accelerations during impacts on the playing field. The researchers observed 249,613 impacts from 423 football players at nine colleges and high schools and collected collision data from participants in other sports. The accelerations during most head impacts (>89%) in helmeted sports caused head accelerations less than a magnitude of 400 m/s2. However, a total of 11 concussions were diagnosed in players whose impacts caused accelerations between 600 and 1800 m/s2, with most of the 11 over 1000 m/s2.
Suppose the average speed while stopping was 4 m/s (not necessarily the correct value) and the collision lasted 0.01 s. Which answer is closest to the head’s stopping distance (the distance it moves while stopping)?
A 10-m-long glider with a mass of 680 kg (including the passengers) is gliding horizontally through the air at 28 m/s when a 60 kg skydiver drops out by releasing his grip on the glider. What is the glider's speed just after the skydiver lets go?
PROBLEM 2
A cube of mass m is placed in a rotating funnel.
(The funnel is rotating around the vertical axis shown
in the diagram.) There is no friction between the cube
and the funnel but the funnel is rotating at just the
right speed needed to keep the cube rotating with the
funnel. The cube travels in a circular path of radius r,
and the angle between the vertical and the wall of the
funnel is 0. Express your answers to parts (b) and (c)
in terms of m, r, g, and/or 0.
(a) Sketch a free-body diagram for the cube. Show
all the forces acting on it, and show the appropriate
coordinate system to use for this problem.
(b) What is the normal force acting on the cube?
FN=mg58
(c) What is the speed v of the cube?
(d) If the speed of the cube is different from what you
determined in part (c), a force of friction is necessary
to keep the cube from slipping in the funnel. If the
funnel is rotating slower than it was above, draw a
new free-body diagram for the cube to show which
way friction…
Circular turns of radius r in a race track are often banked at an angle θ to allow the cars to achieve higher speeds around the turns. Assume friction is not present.
Write an expression for the tan(θ) of a car going around the banked turn in terms of the car's speed v, the radius of the turn r, and g so that the car will not move up or down the incline of the turn.
tan(θ) =
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