Kinesiology 201 Questions
Fluid and Sports Biomechanics
Tony Leyland
School of Kinesiology
Simon Fraser University
Fluid Biomechanics
1. Define lift force? Briefly describe the role lift
force plays in a sport of your choice.
2. Why do the hands in swimming travel in the
curved paths? An example is shown opposite.
[7]
3.
Draw a graph to show the approximate change
in drag force on a ball moving through air in
relation to the ball's velocity. [5]
4.
Does a curve ball really curve? [6]
Sports Biomechanics
These questions are taken from Kin370 exams.
Most are specifically focused on sports
biomechanics but the principles needed to solve
them are relevant to Kin201. However, I may not
have focused on one or two concepts (bounce and spin for example) so on some of the
questions you may have to look at the answers first.
1.
List (do not discuss) the variables that would affect the speed of a baseball after
impact with a baseball bat. Indicate which of these factors the batter realistically
has some control over.
2.
What factors affect (and in what way) the amount of centripetal force required for a
cyclist to negotiate a curve? Explain why the cyclist has to lean into the curve to
maintain balance.
3.
Define the principle of conservation of angular momentum. A diver leaves the
board with an angular momentum of 10 kg.m2.s-1 about his transverse axis, what
would his angular velocity be if he tucks to a position that results in a moment of
inertia of 3.5 kg.m2 about this axis?
Would he be able to rotate about his
longitudinal axis during the dive (answer yes or no)?
1
4. What probable effect would "choking up" on a baseball bat have on the resultant
velocity of a hit ball? Explain why some batters and squash players choke-up on
their respective implements? [6]
5. Briefly explain how a tennis ball with topspin bounces
after an oblique collision with the ground. In returning
such a ball explain what type of bounce you would expect
(relatively high or low). Why? [8]
6. The diagram opposite shows a volleyball spiker during
attack. Explain biomechanically why the legs swing
forward as the shoulder and arm swing forward to impact
the ball. [7]
7. A baseball pitcher throws a curve ball (i.e. he lets it go
with considerable spin). Briefly explain what forces (and
their direction) act on the ball as it travels towards the
batter? [4]
8. Once the blade of a hockey stick hits the ice it is an
advantage to have the hands spread wide on the stick.
Explain why with the aid of a diagram and equations (hint:
think of the torques generated). [5]
9. A gymnast takes off from a springboard as shown
opposite. What factors will affect the magnitude of the
eccentric thrust (torque) he can obtain from the board?
[4]
10. Discuss the factors that contribute to stability of a human
in static equilibrium. [5]
11. The long-jumper opposite uses the “hang” technique where he
moves into the position shown opposite after take-off. Explain
the mechanical reasoning behind adopting this position. [5]
12. The diver shown below leaves the board with a
velocity of 6 m/s at 70o.
a)
b)
c)
Why does he begin the dive with a hurdle (frames 9-14)? [3]
What type of energy is stored in the board? [1]
If is centre of gravity is displaced a total of -1.5 m from take-off until he touches the
water, how much time does his airborne phase take? [5]
2
13. The tennis ball (mass 0.4 kg) shown below has a radius of 4 cm and its centre of
gravity is travelling at a velocity of 10 m/s with an angle of incidence of 25o when it
strikes the ground. In addition the ball is spinning with an angular velocity of –40π
radians/s.
a)
What would be the linear horizontal velocity of the underside of the ball at the point
where the ball strikes the ground? [3]
b) The impact between the ball and the ground
takes 0.1 seconds and the frictional force
exerted upon the ball averages 10 N over this
time period.
The coefficient of restitution
between the ball and the court surface is 0.6.
What is the rebound velocity of the ball (do not
forget to give the angle of rebound)? Note that
although the frictional force is applied at the
ground, its linear effect acts upon the ball’s
centre of gravity. [12]
-40π rad/s
25o
10 m/s
3