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```WARM-UP

What are the two main categories of forces?
WHAT EXACTLY IS A FORCE
A force is a push or pull on an object
 Recall:


A force can act though contact


Spring, normal, applied, friction, etc
A force can act a distance

Gravity, magnetism, electrical
VECTORS

Magnitude and Direction:
PROJECTILE MOTION
http://www.nbclearn.com/portal/site/learn/scienceof-nfl-football
PROJECTILE MOTION

Only one force is
acting on an object
during projectile
motion – gravitational
force


Often air resistance is
negligible
Object follows a
parabolic path
PROJECTILE MOTION

Another way to define projectile motion is
horizontal and vertical motion that is
independent of one another.


Why is that important?
It means we can look at each direction
individually
HORIZONTAL MOTION

No external forces acting in horizontal direction.

This means: constant velocity
VERTICAL MOTION
Gravitational force will pull the object down.
 Direction of this force is from the direction of
acceleration, which is directed down.

Eventually, the projectile will reach a vy = 0 m/s.
 This occurs at the maximum vertical height.
 After this, the ball begins to accelerate in the
downward direction.

VERTICAL MOTION

Increasing velocity in downwards direction:
PUTTING IT ALL TOGETHER

The path of the projectile cannot change its path
without introducing a new force.


Training must prepare an athlete to accurately set
the projectiles path just before release.
NBC – Nick Goepper & the Physics of Slopestyle
Skiing

http://www.nbclearn.com/science-and-engineering-ofthe-2014-olympic-winter-games
PROJECTILE RAMP
CHALLENGE
Day 2
Projectile Motion Challenge

Remember:
Your ramp must be able to be set at 4 different
angles: 15o, 30o, 45o, 90o.
 Once you have finished building your projectile
launcher, you will measure its horizontal distance at
each angle.


You will need to make 3 different measurements at each
angle.
Ramp Challenge

Per Group:
Ramp
 Sketched design of your ramp


Per Person:
Data Table

Pre-Lab Question:
Which angle do you predict
to have the greatest
horizontal displacement?
Questions
sketch? If so, explain the difference AND make a
 Which angle launched the marshmallow the
farthest horizontal distance?
 Which angle do you think produced the greatest
vertical height?
 What other variables could have been introduced
during this experiment? If your results showed
an angle besides 45 degrees for farthest distance,
then what could have been your error?

3 CONCERNS WITH PROJECTILES
Time of flight
 Peak height
 Horizontal displacement

Which sports are concerned with time of
flight? Peak height? Horizontal
displacement?.
SIMULATION


Think of our three major concerns with projectile
motion
Time in flight
 Peak height
 Horizontal displacement

TIME IN FLIGHT
Physics

Depends on:
Sports

Gymnastics
 Figure Skating
 Ski jumping
 Snowboarding (half-pipe)
Initial vertical velocity
 Initial vertical
position



Optimal angle of
projection: 90o

Above 45o
Maximize Time:

Minimize Time:
Volleyball spike
 Tennis smash
 PK kick – soccer
 Baseball throws

PEAK HEIGHT
Physics

Depends on:
Initial height
 Initial vertical velocity


Optimal angle of
projection: 90o
Greater than 45o
 Larger angle = larger
vertical velocity

Sports
High Jump
 Volleyball

HORIZONTAL DISPLACEMENT
Physics

Depends on:
Initial horizontal velocity
 Time in flight:



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Initial vertical velocity
Initial height
Optimal angle of
projection:
Sports
Shot put
 Discus throw
 Long jump
 Baseball hit

45o  there are equal x &
y components
 Smaller angles are
required if initial height is
present.
 Harder to produce vertical
motion than horizontal

Imagine a bowling ball – is it easier to roll it horizontally or throw it up in the air?
Applications In Sports

Golf – Long Irons (1,2, 3)
have a shallow angle on
the club face. They are
designed for distance.
Short irons (7, 8, 9, wedge)
have steeply angled faces
to give height and
“stopping” ability when the
ball lands.
Biomechanics

Speed of release can be maximized in order to
gain distance or time in flight by applying
biomechanical principles such as transfer of
momentum, sequencing and lengths of levers.
By driving with Legs  torso  shoulder  arm 
hand.
 The body acts like a whip imparting tremendous
force to the ball.

Winter Olympics Project
Exit Ticket
What force(s) is/are acting on an object during
projectile motion?
 What implications does projectile motion have on
sports, knowing that you can’t change the
projectile’s path once it is in the air?

```