Conservation of Mechanical Energy

Grade 10 · Physics

Semester 1 | Period 3 | Week 15

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Subject: Physics

Semester: 1

Period: 3

Week: 15

School Name:

Teacher’s Name:

Subject: Physics

Grade Level: Grade 10

Week & Period: Week 15, Period III

Date:

Sub-topic: Conservation of Mechanical Energy

Learning Objectives:
By the end of the lesson, learners should be able to:

  1. State the law of conservation of energy.
  2. Demonstrate the transformation between kinetic and potential energy.
  3. Apply the law to real-life situations and problem-solving.
  4. Carry out experiments showing energy conservation.

Instructional Materials:

  • Pendulum setup
  • Inclined plane with rolling object
  • Weights and pulleys
  • Graph papers and markers
  • Video demonstrations

Anticipation (Warm-Up):
Ask learners:

  • “Can energy be created or destroyed?”
  • “Where does energy go when you swing on a rope and stop moving?”

Building Knowledge:

  1. Law of Conservation of Mechanical Energy:
    • Energy cannot be created or destroyed but can change from one form to another.
    • Total mechanical energy (TME) = Kinetic Energy + Potential Energy remains constant in a closed system without friction.
  2. Examples in Daily Life:
    • Swinging pendulum
    • Roller coasters
    • Waterfalls
  3. Mathematical Expression:

Solved Example:
A ball of mass 2 kg is dropped from a height of 5 m.

  • PE = mgh = 2 × 9.8 × 5 = 98 J
  • At the bottom: KE = 98 J (since PE = 0)
  • Energy is conserved

Experiment:
Title: To demonstrate the conservation of mechanical energy using a pendulum.
Materials: String, bob, protractor, ruler, stopwatch
Procedure:

  1. Suspend bob with string from fixed point.
  2. Pull to one side and release (measure height).
  3. Measure speed at lowest point using stopwatch and displacement method.
  4. Calculate PE at top and KE at bottom.

Observation: PE at top ≈ KE at bottom (neglecting air resistance)
Conclusion: Energy is conserved.

Activities:

  • Measure height and speed of rolling objects down a ramp.
  • Construct a graph showing PE to KE transition.
  • Watch a video of water dams generating electricity.

Assessment:
Oral:

  1. State the law of conservation of energy.
  2. Give two examples of energy transformation.

Written:

  1. A 1.5 kg object falls from 4 m. Find its speed just before hitting the ground.
  2. Describe an experiment to verify energy conservation.

Homework:

  1. Find the KE of an object falling from 6 m.
  2. Why do energy losses occur in real-life situations?

Expanded Notes:

  • Mechanical energy remains constant if no external force acts (e.g., friction).
  • Energy may transform to heat or sound but total quantity remains.
  • Use real-world visuals like wind turbines or dam systems.

Differentiation:

  • Guided experiment worksheets for learners who need structure.
  • Role play: group acts out PE converting to KE.
  • Graphic illustrations for visual learners.

Teacher’s Reflection:

  • Could learners apply the law in solving problems?
  • Were they able to observe and describe energy transitions in experiments?
  • Who needs reinforcement on experimental procedure and analysis?