ER and Ribosomes

1. Newton's First Law: 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 unbalanced force.

• Inertia is the natural tendency of an object to resist changes in its state of motion.

• The more mass an object has, the greater its inertia.

• Example: A book resting on a table will remain at rest unless you push or pull it. When a car suddenly stops, passengers continue to move forward due to their inertia.

2. Newton's Second Law: Law of Acceleration

• The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.

• This law is often summarized by the formula: $F_{\text{net}} = ma$

  • $F_{\text{net}}$ represents the net force (measured in Newtons, N).

  • $m$ represents the mass of the object (measured in kilograms, kg).

  • $a$ represents the acceleration of the object (measured in meters per second squared, $m/s^2$).

• Key implications:

  • A larger net force results in greater acceleration (for a given mass).

  • A larger mass results in smaller acceleration (for a given net force).

• Example: Pushing a light shopping cart requires less force to accelerate it than pushing a heavily loaded one.

3. Newton's Third Law: Law of Action-Reaction

• For every action, there is an equal and opposite reaction.

• This means that when one object exerts a force on a second object, the second object exerts an equal and oppositely directed force on the first object.

• These forces are always equal in magnitude and opposite in direction.

• Important Note: Action and reaction forces act on different objects, so they do not cancel each other out.

• Examples:

  • When a rocket expels gas downwards (action), the gas propels the rocket upwards (reaction).

  • When you push against a wall (action), the wall pushes back on you with an equal and opposite force (reaction).

  • A bird flying: its wings push air downwards (action), and the air pushes the bird upwards (reaction).

  • Walking: your feet push backwards on the ground (action), and the ground pushes forwards on your feet (reaction), propelling you forward.