Problem Solving Laws of Motion

Newton’s First law of motion: Inertia

• Inertia is the tendency of an object at rest to remain at rest, and an object in motion to continue moving at a constant velocity unless acted upon by an external force.
• Imagine trying to push a heavy object like a car; it won’t move easily due to its inertia.

Newton’s Second law of motion: Momentum and Force

• Momentum is the product of an object’s mass and velocity (p = mv). -Force is any interaction that can change the motion of an object (F = ma).
• The greater the force applied to an object, the greater its acceleration, and the more massive an object, the smaller its acceleration when the same force is applied.
• This is evident when trying to push a light object vs a heavy object.

Newton’s Third Law of Motion: Action and Reaction

• For every action, there is an equal and opposite reaction.
• When one object exerts a force on another, the second object exerts a force of equal magnitude but opposite direction on the first object.
• For example, when you press on a wall, the wall pushes back on you with the same force.

Types of Forces:

• Contact forces:

  • Normal force: The force exerted by a surface perpendicular to the surface when an object is in contact with it.
  • Friction: The force that opposes the motion of an object in contact with a surface.
  • Tension: The force exerted by a string, rope, or cable when it is pulled tight.

• Non-Contact forces:

  • Gravitational force: The force of attraction between any two objects with mass.
  • Electrostatic force: The force of attraction or repulsion between two charged particles.
  • Magnetic force: The force of attraction or repulsion between two magnets or between a magnet and a magnetic material.

Equations of Motion:

• First equation of motion (V- U = at)
  • V represents the final velocity, U represents the initial velocity, a represents acceleration, and t represents time.
• Second equation of motion (S = Ut + ½ at²)
  • S represents the displacement (distance moved in a specific direction), Ut represents the initial velocity multiplied by time, and ½ at² represents the additional distance covered due to acceleration.
• Third equation of motion ( V² - U² = 2aS)
  • V represents the final velocity, U represents the initial velocity, a represents acceleration, and S represents displacement.

Special Cases of Motion:

• Motion in a straight line: An object moves along a straight path without changing direction.

• Motion on an inclined plane: An object moves on a surface that is not horizontal, such as a ramp or a hill.

• Motion in a vertical circle: An object moves in a circular path, like a ball on a string.

• Projectile motion: An object is launched into the air at an angle and moves only under gravity.

Conservation of Momentum

• Total momentum of a closed system remains constant, regardless of the internal forces within the system.
• useful when analyzing collisions and explosions.

Impulse:

• Impulse is the product of force and the time over which it is applied (I = Ft).
• A brief, large force can impart the same momentum change as a small force applied over a longer time.