Biomechanics

• Define Newton’s first law?

  Law of inertia

  A body continues in a state of rest or uniform velocity (constant) unless acted upon by an external force
• Define Newton’s second law?

  Law of acceleration. When a force is applied, the rate of change of momentum is proportional to the size of the force and takes place in the direction in which the force acts.

  (Greater the force, greater the acceleration therefore greater the momentum)
• Define Newton’s third law?

  Law of Reaction. For every force that is exerted by one body on another, there is an equal and opposite force entered by the second body onto the first
• Define linear motion?

  Body moves in a straight or curved line with all parts moving in the same direction at the same speed
• Define the term force

  A push or pull that alters the state of motion of a body
• Define velocity

  The rate of motion in a particlar direction
• Define momentum

  The quantity of motion possessed by a moving body
• Define acceleration

  The rate of change of velocity
• Define Action Force

  A force exerted by a performer on a body/object
• Define Reaction Force

  The equal and opposite force to the action force exerted by a second body on the first
• Define Internal force

  Force generated by contractions of the skeletal muscles
• What 5 things does force create?

  1. Motion

  2. Acceleration

  3. Deceleration

  4. Change in direction of a body

  5. Change in shape of a body
• Define Net force

  The sum of all the forces acting on the body. Also known as ‘resultant force’.

  (If net force = 0 then there is no change in motion as all forces are balanced)
• What is the formula for velocity?

  Velocity = displacement / Time taken (units = m/s)
• What is the formula for momentum?

  Momentum = mass X velocity (units = Kg m/s)
• What is the formula for acceleration?

  Acceleration = (final velocity - initial velocity) / time taken (units = m/s/s)
• What is the formula for force?

  Force = mass X acceleration (units = kg m/s/s)
• What are the 2 types of external forces?

  Vertical and Horizontal forces
• What are the 2 verticals forces?

  Weight and Reaction
• What are the 2 horizontal forces?

  Friction and Air resistance
• Define weight

  Gravitational pull that the earth exerts on a body (units = Newtons)
• What is the formula for Weight

  Weight =. Mass X Acceleration due to gravity
• Define Reaction

  Equal and opposite force exerted by a body in response to the action force placed upon it (units = Newtons)
• How is Reaction shown on a free body diagram?

  Shown by a vertical arrow extending upwards from the point of contact with the surface
• Define Friction

  The force that opposes the motion when two surfaces are in contact (units = Newtons)
• How is friction shown on a free body diagram?

  A horizontal arrow extending (usually) in the same direction as motion from the point of contact parallel to the sliding surface
• What 4 factors affect friction?

  1. Roughness of the ground surface

  2. Roughness of the contact surface

  3. Temperature

  4. Size of normal reaction
• Define Air resistance

  Force that opposes the motion of a body travelling through the air and is a form of fluid friction (units = Newtons)
• How can Air resistance be shown on a free body diagram?

  Shown by a horizontal arrow extending against the direction of motion from the centre of mass
• What 4 factors affect air resistance

  1. Velocity

  2. Shape

  3. Frontal cross-sectional area

  4. Smoothness of a surface