Newton's First Law: Law of Inertia

• Newton's laws of motion are three physical laws that describe the relationship between a body and the forces acting upon it, and its motion in response to those forces.

Newton's First Law of Motion: Law of Inertia

• An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an external force.
• This law is often called the law of inertia.
• Inertia is the tendency of an object to resist changes in its state of motion.
• If an object is at rest, it tends to stay at rest.
• If an object is moving, it tends to continue moving with the same velocity.
• Mass is a measure of inertia. The more mass an object has, the greater its inertia.
• A greater force is required to change the motion of an object with a larger mass than one with a smaller mass.
• Examples of inertia include:
  • A stationary object remains still unless pushed or pulled.
  • A moving car stops suddenly, and the passengers continue to move forward.
  • Shaking a tree to dislodge fruits relies on the inertia of the fruits.

Newton's Second Law of Motion: Law of Acceleration

• The acceleration of an object is directly proportional to the net force acting on the object, is in the same direction as the net force, and is inversely proportional to the mass of the object.
• This law can be mathematically expressed as: F = ma, where:
  • F is the net force acting on the object.
  • m is the mass of the object.
  • a is the acceleration of the object.
• If the net force on an object is doubled, the acceleration of the object is doubled.
• If the mass of an object is doubled, the acceleration of the object is halved, assuming the same force is applied.
• The direction of the acceleration is the same as the direction of the net force.
• The unit of force is the Newton (N), which is equal to kg*m/s².
• Examples include:
  • A heavier object requires more force to accelerate it at the same rate as a lighter object.
  • The greater the force applied to a ball, the faster it accelerates.

Newton's Third Law of Motion: Law of Action-Reaction

• For every action, there is an equal and opposite reaction.
• Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.
• These forces act on different objects and are of the same type.
• The action and reaction forces do not cancel each other out because they act on different objects.
• Examples of action-reaction pairs include:
  • When you jump, you exert a force on the Earth, and the Earth exerts an equal and opposite force on you.
  • A rocket accelerates forward by expelling gases backward. The force of the gas on the rocket is the action, and the force of the rocket on the gas is the reaction.
  • When you push against a wall, the wall pushes back on you with an equal force.