Chapter 3 Dynamics with pdf notes

Struggling with 9th class physics chapter 3 dynamics. Here you get easy Sindh board notes, short questions answers, and solved numericals of chapter 3. Learn momentum, Newton laws of motion, centripetal force, and friction with simple language and step by step formulas. Best for SINDH TEXT BOARD 9th class annual exam prep.

DYNAMICS

Dynamics is the branch of physics that deals with the motion of objects and the forces that cause that motion.

FORCE

Force is a push or pull on an object that can change its state of motion, direction, or shape. Its SI unit is newton.

MOMENTUM

Momentum is the quantity of motion an object has. It is equal to mass multiplied by velocity. Its SI unit is kilogram meter per second.

LAW OF CONSERVATION OF MOMENTUM

Law of conservation of momentum states that if no external force acts on a system, the total momentum of the system remains constant before and after collision.

NEWTON’S FIRST LAW OF MOTION

Newton’s first law of motion states that an object at rest stays at rest and an object in motion stays in motion with the same speed and direction unless acted upon by an external force.

INERTIA

Inertia is the property of an object to resist any change in its state of rest or motion. Mass is the measure of inertia.

NEWTON’S SECOND LAW OF MOTION

Newton’s second law of motion states that the force applied on an object is equal to the mass of the object multiplied by its acceleration. Formula is F equals m times a.

NEWTON’S THIRD LAW OF MOTION

Newton’s third law of motion states that for every action there is an equal and opposite reaction.

DIFFERENCE BETWEEN WEIGHT AND MASS

1. Mass is the amount of matter in an object while weight is the force of gravity acting on that mass.
2. Mass is a scalar quantity and remains constant everywhere while weight is a vector quantity and changes with gravity.
3. Mass is measured in kilogram using a beam balance while weight is measured in newton using a spring balance.
4. Mass cannot be zero but weight can be zero at the center of earth or in space.

UNIFORM CIRCULAR MOTION

Uniform circular motion is the motion of an object moving in a circular path with a constant speed but its direction keeps changing.

CENTRIPETAL FORCE

Centripetal force is the force that acts on an object moving in a circle and is directed toward the center of the circle. It is needed to keep the object in circular motion.

CENTRIFUGAL FORCE

Centrifugal force is an apparent outward force experienced by an object moving in a circular path, as seen from the rotating frame of reference.

DIFFERENCE BETWEEN CENTRIPETAL FORCE AND CENTRIFUGAL FORCE

1. Centripetal force acts toward the center of the circle while centrifugal force appears to act away from the center.
2. Centripetal force is a real force while centrifugal force is a pseudo or fictitious force.
3. Centripetal force is observed in an inertial frame while centrifugal force is observed in a rotating frame.

APPLICATIONS OF CENTRIFUGE

1. Used in laboratories to separate components of blood like plasma and red blood cells.
2. Used in washing machines to remove water from wet clothes during spin cycle.
3. Used in dairy industry to separate cream from milk.
4. Used in oil industry to separate impurities from oil.
5. Used in DNA testing to separate DNA from other cell components.

FRICTION

Friction is the force that opposes the relative motion between two surfaces in contact.

TYPES OF FRICTIONS

1. Static friction acts on objects that are not moving.
2. Sliding or kinetic friction acts on objects that are sliding over each other.
3. Rolling friction acts when an object rolls over a surface.
4. Fluid friction or drag acts on objects moving through air or liquid.

ADVANTAGES OF FRICTION

1. Friction helps us walk without slipping.
2. It allows vehicles to move and stop using brakes and tires.
3. It helps us hold and grip objects.
4. It is used to light a matchstick.

DISADVANTAGES OF FRICTIONS

1. Friction causes wear and tear of machine parts.
2. It reduces the efficiency of machines by producing heat.
3. It requires extra energy to overcome friction during motion.
4. It can cause damage to roads and shoe soles over time.

WAYS OR METHODS TO REDUCE FRICTION IN OUR NORMAL DAILY LIFE

1. Use lubricants like oil or grease between moving parts.
2. Use ball bearings and wheels instead of sliding objects.
3. Polish and smooth the surfaces to make them less rough.
4. Use streamlining in vehicles and ships to reduce air and water resistance.

Practice all short questions and numerical problems of dynamics chapter 3 daily for full marks. Remember formulas F = m x a, p = m x v, and W = m x g. These Sindh text board 9th class physics notes will help you score better in your board exam. Save and share with your class fellows.

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