Objects begin to move when some type of force is applied on them.  Force can be viewed as a push or pull that may change or tend to change the state of motion of a body (an athlete) or object (javelin, discuss, football, barbell).  Forces can increase or decrease velocity, and cause an object to change directions.  A net force is defined as the difference between the applied force and resistive  force. In order to start or stop an object, a positive force (an applied force greater than the resistive force) must be applied.  If the net force is negative, there is no change in the state of the object. That is, the object remains stationary or continues in a state of constant motion. For example, if one attempts to lift a 40 pound box and the net result is no movement, then the net force must of been negative. However, one could say that there is a tendency for the box to be set into motion.   In other words, it is closer to moving when you are attempting to lift it than if you didn’t pull on it at all.   Of course, if the box is lifted, than the net force must of been positive.

Recall that force is a vector quantity.  It possesses both magnitude and direction. In addition, force has an exact point of application.  All three characteristics must be considered when attempting to describe force.  An object will experience linear motion if a force is applied through the object’s center of gravity. In contrast, an object will experience rotatory motion if the force is applied away from the center of gravity.  Sir Isaac Newton observed that motion is related to force.  He therefore formulated three laws of motion that help us understand why objects move as they do.  The three laws are accepted as universal truths to explain how force impacts movement.

The primary purpose of this lab is to apply general principles of mechanics to motion.  There will be series of questions focusing on Newton’s laws in order to better understand human locomotion and motion of objects.

During this laboratory experience there will be a series introductory questions that you must answer as a group.  Once these questions are answered, you will be required to visit various stations in the lab and study specific aspects of the different movement patterns posted at each station.  A series of questions will be available at each station.  As a group, address each question.  The instructor will be available to engage in any discussion.
 
 

Newton’s Laws applied to motion.

A.   State each of Newton’s laws as applied to linear motion.

1.
 
 
 

2.
 
 
 
 

3.
 

B. State each of Newton’s laws as applied to angular motion.

1.
 
 
 
 

2.
 
 
 
 

3.
 
 
 
 
 
 
 
 
 

Station one.  Jumping.    Long Jump Take Off.
Long jump is a motor skill which falls under the general movement pattern of jumping. The actual long jump event consists of the following general phases: run up (approach), take off, flight, landing.  The following image focuses on the take off.

A.  In general, describe the main joint actions of the lower extremities.  Include in your description the major plane and axis.
 
 
 

B.  Discuss the application of Newton’s laws of linear motion to the long jump take off.
 
 
 

C.  What factors will determine the trajectory of long jumper.
 
 
 
 
 

Station two.   Child running.

Running, to a large degree, is a speeded up walking pattern.  In general, successful running requires alternate coordination of the arms and legs, a vertical or somewhat forward inclination of the body as a whole, and optimal application of force to the ground.  There are many aspects of the running pattern which can account for poor movement.   Study the images of the child runnner.

A.  What running pattern deviations are present in the images.
 
 

B.  Discuss how the deviations noted above take away from effective running. Consider arm and leg actions, When possible apply any of Newton’s laws to discuss why the deviations would take away from effective movement.
 
 

Station three.  Striking.  Baseball Hit.  Hitting is a striking pattern.  In hitting, one gives momentum (or impetus) to an object (like a ball, or perhaps an opponent) by swinging or striking at the object with the hand, arm or some implement held in the hand (or hands).  The hitting pattern is vary similar to a throwing pattern.  Some adjustments, of course,  must be made in the hitting pattern in order to effectively make contact with an object (i.e., striking a ball).  Study the images of the baseball player hitting the ball.

A.  What is the action of the trunk.  Identify the plane and axis.
 

B.  Define momentum.
 

C.  Discuss transfer of momentum. Start with the application of force to the ground by the batters feet.
 

D.  What are possible outcomes of using a heavier bat.
 
 

C.  What can a batter do to hit a ball as hard as possible.

A.  Define potential and kinetic energy. When is potential and kinetic energy the greatest and least?
 
 

B.  Compare the pike to the tuck position.   Which position results in faster spinning? Explain your answer.
 

C.  Does Newton’s law of action/reaction apply to any of the images?
 
 
 

 
Station five.  Spinning objects and rebound.

You will find several tennis balls to play with.  Perform the following actions, (1) apply topspin to the ball and observe the rebounding action, and (2) apply backspin to the ball and observe the rebounding action.  You may need to perform the above actions several times.

A.  What did you observe about the rebound for the  topspin and backspin actions?
 

B.  Explain your observations of rebound with the use of force and velocity vectors.
 

Station six.  Throwing.   Throwing involves a movement pattern in which an object (like a ball, discuss, javelin) is propelled into the air by the hands and arms.  An object may be released by throwing overhead, sidearm, or underhand.  Certainly, the entire body may be used in the throwing action.  The extent to which the body is utilized depends upon the mechanical goal of the throw (i.e., distance, speed, accuracy) and maturation level of the thrower.  Factors important in throwing include opposition of arms and legs, and sequential involvement and coordination of body segments.  Study the various images of throwing.
 

A. Hammer throw.   In the hammer throw, there is a battle between inertia and centripetal force.  What does this mean?
 
 

B.  Child throwing a ball.   Study the four developmental stages of throwing.  What is your general observation of the four stages?  Why would the child in image  d   be more likely to throw the ball further compared to image   a.?
 

C.  Football throw.   What impact does grip have on throwing a football.   Compare images  a
and   b.