Grade 10 Physical Science Lesson Plans

Grade 10 Physical Science Lesson Plans

GRADE 10 SUBJECT

Physical Sciences

WEEK

34 Lesson 1 TOPIC

Gravitational Potential Energy

LESSON SUMMARY FOR: DATE STARTED:

DATE COMPLETED:

LESSON OBJECTIVES

At the end of the lesson learners should be able to: Define gravitational potential energy Determine gravitational potential energy of an object

TEACHING and LEARNING ACTIVITIES

TIME: 60 minutes

1. TEACHING METHOD/S USED IN THIS LESSON: Demonstration ; observation , question and answer method

2. LESSON DEVELOPMENT

2.1 Introduction

a) PRE-KNOWLEDGE learners need understanding of the following: (i) Different forms of energy (ii) Potential energy of an object

b) BASELINE ASSESSMENT (educator to design a worksheet/ transparency or write questions on the board [preferably a worksheet to save time] to gauge the learners memory of their relevant prior knowledge) [5 min]

QUESTIONS for the BASELINE ASSESSMENT i) List five forms of energy ii) Define potential energy iii) Give three examples of potential energy iv) What are the factors that affect the gravitational potential energy of an object

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c) Do corrections i) Sound, light, heat, chemical energy, kinetic energy, potential energy etc. ii) Potential energy is the energy due to object's position or state.(stored energy) iii) Electrical potential energy, gravitational potential energy and Chemical potential energy iv) Mass and the height of an object

Grade 10 Physical Science Lesson Plans

2.2 Main Body (Lesson presentation) [30 min]

Gravitational potential energy is the energy an object ha due to its position in a gravitational field relative to some reference point. Gravitational potential energy (Ep) is a scalar quantity and is measured in Joules (J). * Some books use the symbol PE or U for gravitational potential energy

where = gravitational potential energy (measured in joules, J), m = mass of the object (measured in kg) g = gravitational acceleration (9,8 m?s-2) h = perpendicular height from the reference point (measured in m) Reference point is the zero energy level. Example of this reference point is the ground.

Gravitational potential energy (EP) of an object is directly proportional to the mass of an object. EP m; and Gravitational potential energy (EP) of an object is directly proportional to the height of an object EP h

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Grade 10 Physical Science Lesson Plans

As the money back moves upwards: Kinetic energy decreases and gravitational potential energy increases Kinetic energy decreases is converted into gravitational potential energy increases

As the money back moves downwards: Kinetic energy increases and gravitational potential energy decreases Kinetic energy decreases is converted into gravitational potential energy increases



Example

A brick with a mass of 2kg is lifted to the top of a 5 m high roof. It slips off the roof and falls to the ground. Calculate the gravitational potential energy of the brick a) at the top of the roof b) on the ground once it has fallen.

Solution

a)EP = mgh = 2(9,8)5 = 98 J

b) On the ground, the height is zero. Therefore gravitational potential energy is zero

Learners activities 10 min (Consider g = 9.8 ms-2 near the surface of the Earth.)

1)

Climbing a vertical rope is difficult. You have to lift your full body weight with your arms. If your mass is 60 kg and you climb 2.0 m, by how

much do you increase your gravitational potential energy?

2)

A block of bricks is raised vertically to a bricklayer at the top of a wall using a pulley system. If the block of bricks has a mass of 24 kg,

what is its weight when it is raised 3,0 m? Calculate its increase in gravitational potential energy when it reaches the top of the wall.

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Grade 10 Physical Science Lesson Plans

3)

Travelling in a mountainous area, a bus of mass 3 tonnes reaches the edge of a steep valley. There is a 1 km vertical drop to reach the

valley below, but 20 km of road to get there. What gravitational potential energy will the bus lose in descending to the valley bottom?

4)

Assuming the bus in question 3 does not change its cruising speed on the way down, where does the gravitational potential energy go?

Why is there a risk of brake failure in this situation?

5) A basketball player, who is 2m tall, holds a 500g netball 0,3 m above his head and shoots for the goal net which is 3 m above the ground.

Assume that his feet do not leave the ground as he shoots for a goal and answer the following questions:



Corrections [7 min]

1

E p = mgh

= 60 x 9.8 x 2

= 1176 J

2

Weight = mg

= 24 x 9.8

= 235. N

What is the gravitational potential energy of the ball:

5.1. when it lands on the ground after the goal is scored? 5.2. when he is about to shoot it into the net? 5.3. when it gets right into the net?

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Change in EP = mgh = 24 x 9.8 x 3.0 = 705.6 J

Grade 10 Physical Science Lesson Plans

3

Change in EP = mgh

= 3000 x 9.8 x 1000

= 2.94 x 107 J

4

Since the bus gains no kinetic energy (its speed stays the same) it must be using its brakes, and all the gravitational potential energy lost by

the bus in converted to heat in the brakes. There is a risk of brake failure if the brakes overheat.

5.1 When the ball lands on the ground after the goal is scored, the height of the ball is 0 m. And the gravitational potential energy is zero (0) J 5.2 The height from which the ball is shot h =( 2 + 0,3)m = 2,3 m , but the mass must be converted to kg. m = 500/1000 = 0,5 kg

EP= mgh = (0,5)(9,8)(2,3) = 11,27 J

5.3

EP= mgh

= (0,5)(9,8)(2,3)

= 14,7 J

3. Conclusion Activity to Reinforce lesson(Educator may summarise the main aspects of the lesson).[5 min.]

HOMEWORK QUESTIONS/ ACTIVITY (educator must give learners a few questions to answer at home by either writing them on the chalkboard or giving an exercise from the prescribed textbook) [30 min]

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