Notes, summaries, assignments, exams, and exercises for Physics for Secondary education

Understanding Force, Motion, and Newton's Laws

Force and Motion

Every action force is able to alter the state of movement or rest of bodies, or produce in them some deformation. A vector is a directed line segment.

Elements of the force vector:

• Point of application: The point on which force is applied.
• Magnitude: The intensity of the force.
• Direction: The line on which the force vector acts.
• Sense: Indicates which of the two possible orientations of force is adopted.

Types of Forces

Weight of a body: Gravitational traction force exerted by the Earth.

Power system: A set of forces acting on a body, equivalent to a single imaginary force.

Resultant force: The force on a body that produces the same effect as the set of all the forces acting; the vector sum...

Basic Laws of Cartesian Physics

Descartes invokes God to explain extension and motion: God is the creator of matter and of a certain amount of motion that remains constant, because God is unchangeable both in being and in operation. He therefore regards the universe as a closed system. He formulates three fundamental laws:

Three Fundamental Laws of Motion

1. Law of inertia: Every body tends to remain in its state of rest or of uniform motion in a straight line unless acted on by an external force.
2. Law of straight-line motion: Any body in motion tends to continue moving in a straight line unless an external force intervenes; otherwise there would be no reason to explain a deviation.
3. Law of conservation of motion: Motion is not lost in collisions between

What is Force?

Force is a push or pull that can deform an object or change its state of rest or motion.

Types of Forces

• Contact
• Non-contact
• Instantaneous
• Constant

Formula of Force

F = m • a

Difference Between Force and Weight

Weight is a force. Everything on Earth is pulled down towards the ground by gravity. The weight of an object is how hard gravity pulls down on it.

Larger objects get pulled more strongly, so they weigh more than smaller objects. When scientists want to talk about how much stuff is inside something, they talk about mass.

Causes of Force

Forces arise when two or more bodies come into contact. For example, when there is a crash or when you push a door.

Bodies, even if they are not in contact, exert a force on others. For example, the...

Static electricity:

• There are electrostatic forces between particles or objects with a positive or a negative charge.
• Charge is due to the surplus or defect of electrons.
• Like charges repel each other while opposite charges attract each other.
• Electric charge is measured in coulomb (C) and has the symbol Q.
• When there is an imbalance of positive and negative charge, we get a force between the charges according to Coulomb's law.

Electric current:

• Electric current is a flow of electrons or other charges through a material.
• Conductor: Electrons can move easily through the conductor.
• Insulator: It is very difficult for electrons to move through the material. The electrons are not free to move and form bonds.

Electrical Magnitudes:

• Potential difference is

• Thermal energy is the energy that is exchanged between two bodies or systems of matter that have different temperatures. Thermal energy is also exchanged when a body changes from one physical state to another.

• Kinetic energy (Ec) is the energy of a body in motion. It depends on the mass and the speed of the body.

• Potential energy (Ep) is the energy of a body determined by its position. It depends on the body’s mass and position

• Gravitational Potential Energy
• Elastic potential energy

• Electrical energy is energy produced by the movement of charged particles (electrons), due to a potential difference.

• Radiant energy is energy carried by the electromagnetic waves, such as light, radio waves, microwaves, X-ray or γ rays. It’s called radiation. 

• Chemical

Uniformly Distributed Load (UDL) and Varying Load (UVL)

Converting Distributed Loads to Equivalent Point Loads

1. Uniformly Distributed Load (UDL)

Definition: A load that is evenly spread across a specific length ($L$) of a beam or structure.

Magnitude of Equivalent Point Load ($W$):

$$W = w \times L$$

• $w$: Intensity of UDL (N/m or kN/m)
• $L$: Length over which the UDL acts

The equivalent point load $W$ acts at the geometric center of the distributed load (at $L/2$ from either end).

UDL Diagram and Equivalent Point Load:

|‾‾‾‾‾‾‾‾‾‾|
| w N/m |
|___________|

Equivalent:

| | ↓ W = w × L
| | (at L/2)
|_______________

2. Uniformly Varying Load (UVL)

Definition: A load whose intensity varies linearly across the beam length, typically...

1. Converging or diverging ability of a lens or a mirror is defined as its focal power.
2. This implies that the greater the power of any spherical mirror or lens, the more its ability to converge or diverge the light that passes through it.
3. In the case of a convex lens or concave mirror, the greater the convergence, the shorter the focal length, as shown in the figure.
4. Similarly, in the case of a concave lens or convex mirror, the greater the divergence, the shorter the focal length.
5. This explains that the focal power of any spherical lens or mirror is inversely proportional to the focal length.
6. Hence, the expression for focal power is given by the formula, P = 1f.

Question 4.
At which positions of the objects do spherical mirrors produce (i) diminished...

Thermal Energy and Matter

Work and Heat

Heat is the transfer of thermal energy from one object to another because of a temperature difference. Heat flows spontaneously from hot objects to cold objects. Temperature is a measure of how hot or cold an object is compared to a reference point. On the Kelvin scale, absolute zero is defined as a temperature of 0 kelvins. As an object heats up, its particles move faster, on average. The average kinetic energy of the particles increases. One way that heat flows is by the transfer of energy in collisions. On average, high-energy particles lose energy. Low-energy particles gain energy.

Thermal Energy

Thermal energy is the total potential and kinetic energy of all the particles in an object and depends on...

Properties of Matter

Matter occupies space that can be measured. Two pieces of matter cannot occupy the same space.

The objects that surround us and which have defined limits are known as material bodies. If the limits are not precise, then we speak of material systems.

Properties of Matter

All the qualities of a material body are properties of matter.

• Extensive properties of matter: Extensive properties depend on the size of the material body we are observing, such as mass and volume.
• Intensive properties of matter: Intensive properties are not dependent on body size observed. They serve to differentiate material bodies. We say that two material bodies are composed of the same substance when they have the same intensive properties.

Measurement

What