Mechanics (Part – 2)

which states:

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

Explanation:

1. Action: When the cannon is fired, it exerts a force on the cannonball, pushing it forward at high speed.

2. Reaction: The cannonball exerts an equal and opposite force on the cannon, pushing it backward.

This backward movement of the cannon is called recoil.

Explanation:

This means that:

• Whenever one object exerts a force on a second object,

• The second object exerts an equal and opposite force back on the first object.

Examples of Newton’s Third Law:

1. Cannon and Cannonball: When the cannon fires the cannonball forward (action), the cannon recoils backward (reaction).

2. Walking: When you push back on the ground with your foot (action), the ground pushes you forward (reaction), allowing you to move.

3. Balloon Rocket: When air rushes out of a balloon (action), the balloon flies in the opposite direction (reaction).

4. Jumping: You push down on the ground (action), and the ground pushes you up (reaction), allowing you to jump.

• This law of Newton is also called the law of action and reaction.
• In fact, it works on the principle of conservation of momentum.

Explanation:

• When you hit the nail with a hammer (action), the nail tries to push into the wood.

• According to Newton’s Third Law, the nail (and wood) exerts an equal and opposite reaction force on the hammer.

Now, because the wooden frame is freely suspended (not fixed to anything), it moves backward instead of resisting the nail's entry.

• It expresses that for every action there is an equal and opposite reaction.
• That is, if one object exerts a force on another body, then that object or body also exerts the same force on the first object.

The movement of a horse-drawn carriage is an example of Newton’s Third Law of Motion.

Explanation:

When the horse pulls the carriage forward, the following actions take place:

• The horse pushes backward on the ground with its hooves (action).

• The ground pushes forward on the horse with an equal and opposite force (reaction), causing the horse (and carriage) to move forward.

At the same time:

• The horse exerts a forward force on the carriage through the harness.

• The carriage exerts an equal and opposite backward force on the horse.

But because the force of the ground pushing the horse forward is greater than the carriage’s resistance, the whole system moves forward.

This law states that for every action, there is an equal and opposite reaction.

How it applies:

1. Rocket Engines:

   • Action: Hot gases are expelled backward at high speed.

   • Reaction: The rocket is pushed forward with equal force (thrust).

2. Jet Engines:

   • Action: Air is taken in, compressed, mixed with fuel, and exhaust is expelled backward.

   • Reaction: The jet moves forward.

3. Deflating Balloons:

   • Action: Air rushes out of the open end of the balloon.

   • Reaction: The balloon moves in the opposite direction.

An object's acceleration is the net result of any and all forces acting on the object, as described by Newton's Second Law.

Newton's second law of motion can be formally stated as follows:

"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."

       f= ma

According to this, the gravitational force acting between two objects is directly proportional to the product of the masses of those objects and inversely proportional to the square of the distance between them.

• Magnetic force is absent in the oil droplet experiment.
• In 1913, the American physicist R. A. Millikan performed the pioneering oil-drop experiment to measure an electron's charge precisely.
• He found that the charge on an oil droplet was always an integral multiple of an elementary charge 1.602 × 10⁻¹⁹ С.
• Millikan's experiment established that electric charge is quantized.