http://img1.liveinternet.ru/images/attach/b/3/21/199/21199667_11225732.jpg
|
FBD of Newton's 1st Law
The following is a visual representation of Newton's First Law of motion during a leap. The law states that an object will remain at rest or in motion unless a force acts on it. In the FBDs, the dancer is applying force on the ground and the Earth is applying an equal force on the dancer. Accelerating into the air, friction is present between the dancer's foot and the floor. Once in the air, these forces cause the dancer to begin move upwards. Then, while the dancer is in the air, the sole force of gravity is allowing the dancer to continue moving. As the dancer lands back on the floor, the force they are applying to the floor is equal to the force of Earth on the dancer. Once, again friction is acting on the dancer's feet. These forces are what causes the dancer to stop moving and remain at rest.
Net force in the y = Force normal - Force Earth = 0 Net force in the x = Force friction Net force in the y = Force Earth = -9.8 m/s/s Net force in the y = Force normal - Force Earth = 0 Net force in the x = Force friction |
FBD of Newton's 2nd Law
This FBD represents Newton's Second Law of Motion. When a dancer is turning, the force(s) applied (angular momentum, angular velocity, torque) allow the dancer to turn. In addition, friction has an affect on the horizontal forces that are allowing the dancer to turn. The forces in the y direction are balanced, therefore the net force in the y direction is 0. This can be proved because when a dancer is turning, he or she is neither floating or falling into the Earth.
Net force in y = Force Normal - Force Earth = 0 Net force in x = Force Applied - Force Friction = mass * acceleration On a side note: Torque can be determined through an equation almost identical to Newton's Second Law. Torque = distance between feet * angular acceleration |
http://s4.favim.com/orig/49/arabesque-ballet-polina-semionova-Favim.com-441224.jpg
|
FBD of Newton's 3rd Law
The following FBD is a representation of Newton's Third Law. This diagram is a representation of a dancer as he or she balances. Whether it be two feet on the floor, one foot on the floor or on pointe, force normal is equal to the force of Earth. This is the case because of Newton's Third Law, which states that there are equal and opposite forces. The floor is applying the same amount of force to the dancer, as the Earth is applying to the dancer. Net Force = Force Normal - Force Earth = 0 |