Biophysics for Physical Therapy Students

Biophysics (1) for Physical Therapy Students

• Course is taught by Dr. Mohammed Sadek, Lecturer of Physics, Basic Sciences Department, Faculty of Engineering, Sinai University.

Lecture Objectives

• Meaning of Force
• Four Fundamental Forces
• Difference between Weight and Mass
• Difference between Velocity and Acceleration
• Newton's Laws

Forces

• Force is an interaction between two bodies or a body and its environment.
• A force is a push or a pull.
• A force is a vector quantity with magnitude and direction.

Four Common Types of Forces

• Normal Force (n): A perpendicular force exerted by a surface on an object resting on it.
• Friction Force (f): A parallel force exerted by a surface opposing motion. It acts in addition to the normal force.
• Tension Force (T): A pulling force exerted by a rope, cord, etc.
• Weight (w): A force due to gravity acting on an object with a long-range effect

The Four Fundamental Forces

• Gravitational Force
• Weak Nuclear Force
• Electromagnetic Force
• Strong Nuclear Force

Difference Between Weight and Mass

• Mass: A constant property of an object, the same everywhere, and cannot be zero. Measured in grams or kilograms.
• Weight: A force influenced by gravity. Weight changes with location, can be zero in the absence of gravity, and is measured using a spring balance in newtons, a unit of force. Example: weight on earth (9.80 N) vs on the moon (1.62 N) for a 1.00 kg object.

Difference Between Velocity and Acceleration

• Velocity: Speed in a given direction, measured in m/s.
• Acceleration: Change in velocity over time (rate of change), measured in m/s². Acceleration of an object is proportional to the net force acting on it, and inversely proportional to the object's mass (a = F/m). Acceleration could be given as a vector quantity, too.

Newton's Laws

• Newton's First Law: An object at rest stays at rest and an object in motion stays in motion with the same velocity unless acted upon by an unbalanced force. In other words, if the net force is zero, acceleration is zero.
• Newton's Second Law: The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (F = ma). Force is a vector quantity and this means that acceleration will occur in the same direction.
• Newton's Third Law: For every action, there is an equal and opposite reaction. Forces come in pairs.

Momentum

• Momentum (p) is a product of mass and velocity (p = mv), and is a vector quantity.
• The net force is equal to the rate of change of momentum over time (ΣF = d(mv)/dt).