Lesson Notes By Weeks and Term v3 - Senior Secondary 1

Lesson Video

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Performance objectives

• Define and give examples of work, energy, and power.
• Calculate work done and gravitational potential energy.
• Calculate power in watts.
• Identify types of energy (Kinetic and Potential).
• Explain energy transformation and state the Law of Conservation of Energy.

Lesson summary

Explain work,energy and power and giveexample of each Calculate:The workdone,given a for ce and displacement itproduces in itsdirection.The gravitationalpotential energyat a height habove a givenreference plane Calculate the lower in watts,given an appliedforce and the time it takes to produce adisplacement identify the typeof energypossessed by abody under givenconditions. distinguishbetween kineticenergy and potential energy identify energytransformationfrome one for minto another State the law of conservation of energy

Lesson notes

Definition: In physics, work is done when a force causes a displacement of an object in the direction of the force. For work to be done, two conditions must be met: A force must be applied to the object. The object must undergo a displacement. There must be a component of the force in the direction of the displacement.

Formula: If a constant force, F, acts on an object and causes a displacement, d, in the direction of the force, the work done (W) is given by: W = F × d If the force is applied at an angle (θ) to the direction of displacement, only the component of the force parallel to the displacement does work. W = Fd cosθ Where: W = Work done (in Joules, J) F = Magnitude of the force (in Newtons, N) d = Magnitude of the displacement (in metres, m) θ = Angle between the force and the displacement vector.

Unit of Work: The SI unit of work is the Joule (J). One Joule is the work done when a force of one Newton moves an object through a distance of one metre in the direction of the force (1 J = 1 Nm).

Examples: A farmer pushing a wheelbarrow loaded with cassava tubers over a distance. A student lifting a textbook from the floor to a table. A technician pulling a heavy generator across a workshop floor.

Conditions for Zero Work Done: If there is no displacement (d = 0), e.g., pushing a stationary wall. If the force is perpendicular to the displacement (θ = 90°, cos 90° = 0), e.g., a person carrying a bag walking horizontally (the lifting force is perpendicular to horizontal displacement). If no force is applied (F = 0).

Definition: Potential energy is the energy stored in an object due to its position or state. a)

Gravitational Potential Energy (GPE): This is the energy an object possesses due to its height above a reference level (e.g., the ground).

Formula: GPE = mgh Where: GPE = Gravitational Potential Energy (in Joules, J) m = mass of the object (in kilograms, kg) g = acceleration due to gravity (approximately 9.8 m/s2 or 10 m/s2 in calculations for simplicity) h = height of the object above the reference plane (in metres, m)

Examples: Water stored in the reservoir of the Kainji Dam at a high altitude has GPE, which can be converted to electrical energy. A bag of rice placed on a high shelf in a market stall. A child at the top of a slide. b)

Elastic Potential Energy: Energy stored in elastic materials when they are stretched or compressed (e.g., a stretched catapult, compressed spring). (Briefly mention for awareness).

Definition: Kinetic energy is the energy an object possesses due to its motion. Any moving object has kinetic energy.

Formula: KE = 1⁄2mv2 Where: KE = Kinetic Energy (in Joules, J) m = mass of the object (in kilograms, kg) v = speed (velocity) of the object (in metres per second, m/s)

Examples: A moving commercial motorcycle ("okada") or tricycle ("keke Napep"). A fan blade rotating. Wind blowing across a field, turning a windmill. A football kicked by a player. | Feature | Kinetic Energy (KE) | Potential Energy (PE) | | :-------------- | :------------------------------------------------ | :------------------------------------------------------ | | Definition | Energy possessed due to motion. | Energy possessed due to position or state. | | Dependency | Depends on mass and speed (KE = 1⁄2mv2). | Depends on mass, gravity, and height (PE = mgh) or state (e.g., stretched spring). | | Example | A running athlete, a moving vehicle. | Water in an overhead tank, a yam on a high shelf. | | Transformation | Can be converted to PE (e.g., a ball thrown upwards slows down and gains height). | Can be converted to KE (e.g., a falling object gains speed and loses height). |

Real-life applications

Electricity Generation (Hydroelectric Power): Nigeria's major power plants like Kainji Dam, Shiroro, and Jebba operate on the principles of work, energy, and power. Water stored at high altitudes (potential energy) falls, converting to kinetic energy, which then turns turbines (mechanical work) to generate electricity (power). Students can appreciate the physics behind their electricity supply and the nation's energy infrastructure.

Agriculture and Rural Development: Manual Labour: Farmers lifting bags of produce, tilling soil, or drawing water from wells all involve work and energy. Understanding these concepts helps in designing more efficient tools or techniques to reduce drudgery (e.g., using pulleys or simple machines to reduce the force required).

Irrigation and Pumping: Many farmers use petrol or diesel pumps to irrigate their farms. The power rating of these pumps determines how quickly they can lift water from a source to the farmland, directly relating to the concept of power (rate of doing work).

Transportation and Vehicle Performance: The movement of "okadas," "keke Napeps," buses, and cars illustrates kinetic energy. The power of their engines determines their acceleration and ability to climb hills (doing work against gravity). Understanding energy conservation can inform discussions on fuel efficiency and safety. For instance, the kinetic energy of a fast-moving vehicle needs to be dissipated as work done by brakes to bring it to a stop. ---

Teacher activity

• Begin by asking students about daily activities that involve effort, movement, or using machines. Examples: carrying market goods, farming, pumping water from a well, driving a car, using a blender. Introduce these as examples of "work being done," "energy being used," or "powering machines."

Evaluation guide

• The evaluation will be continuous throughout the lesson (formative) and formally assessed at the end (summative) to ensure all performance objectives are met.
• Formative Assessment Strategies:
• Observation: Monitor students' engagement during discussions and practical activities. Observe their ability to take notes and participate.
• Question and Answer: Pose direct questions to individuals or the class to check understanding of definitions, units, and simple concepts.
• Short Quizzes/Exit Tickets: Ask 1-2 quick questions at the end of a segment (e.g., "What is the unit of work?").

Reference guide

• Chart showing the displacement of abox by a for ceacting:- horizontally- at an angle
• Chart showinglifting of an objectthrough a height hto show work doneagainst gravity.
• Chart showing afalling objectthrough a height has work done by gravity.
• Stop watch, meterrule to measurepower (e.g.climbing of a staircase).
• Chart showingenergy conversions