# Lesson Notes By Weeks and Term - Junior Secondary School 2

ENERGY TRANSFER WHEN WORK IS DONE

TERM: 2nd TERM

SUBJECT: BASIC SCIENCE

CLASS:  JSS 2

REFRENCE

• Precious seed BASIC SCIENCE FOR JUNIOR SECONDARY SCHOOLS BOOK 2

WEEK FOUR                                                                    DATE:………………..

TOPIC: ENERGY TRANSFER WHEN WORK IS DONE

If you put energy into an object, then you do work on that object (mass).

If a first object is the agent that gives energy to a second object, then the first object does work on the second object. The energy goes from the first object into the second object.

At first we will say that if an object is standing still, and you get it moving, then you have put

energy into that object. The object has kinetic energy as a result of your work. You pushed it through a displacement, you did work on the object.

• A  golfer uses a club and gets a stationary golf ball moving when he or she hits the ball. The club does work on the golf ball as it strikes the ball. Energy leaves the club and enters the ball. This is a transfer of energy. Thus, we say that the club did work on the ball
• The work done by the weight lifter in lifting the weights, in order to do this work energy had to be transferred. Chemical energy from food eaten by the weight lifter was transferred to  joules of gravitational potential energy to the barbell.
• Thus the amount of work done is equal to the energy transferred from one form to another. In order to lift the barbell above his head the weight lifter need to apply a force which opposes the downward acting force of gravity on the mass of the barbell.
• No mechanical work occurs in the man's body while he holds himself motionless. There is a transformation of chemical energy into heat, but this happens at the microscopic level inside the tensed muscles. Right: When the woman lifts herself, her arms do positive work on her body, transforming chemical energy into gravitational potential energy and heat

ENERGY CONVERSION            with examples

Chemical energy   to Heat energy        Match, Rockets

Electrical  energy  to Sound energy        Electric Bell, Loud speaker

Electrical energy   to Mechanical        Electrical fan

Chemical energy   to Electrical         Dry Cells (Batteries)

Light energy   to Chemical energy        Green plant leaves

Mechanical energy   to Heat energy        Brakes of a car/bikes

Chemical energy  to mechanical energy     Human body/car

Mechanical energy to sound energy        Drum /hand bell

Sound energy  to electrical energy        Microphone

Light energy   to electrical energy        Solar cell

EVALUATION

1. List five examples of energy conversions and their converters in each case.
2. Explain the term exercise physiology.

GENERAL EVALUATION

1. What is the energy transfer when a golfer uses a club and gets a stationary golf ball moving when he or she hits the ball? The club does work on the golf ball as it strikes the ball. Energy leaves the club and enters the ball?
2. List five examples of energy conversions and their converters in each case.
3. Explain  exercise physiology.

WEEKEND ASSIGNMENT

1. The mainspring to all life activities is the A. energy    B. power C.  work D. force
2. The device which can convert solar energy to electricity is the A.  electro magne
1. photo voltaic solar panel     C.  turbine D. dynamic
1. The chlorophyll in plants uses ---- to produce energy. A.  light B.  plant C.  sun
1. atmosphere.
1. If you put energy into an object, then you do ---on that object. A. work B. power
1. energy D. force
1. The law of conservation of energy is also known as ---- A. First law of thermodynamic B. law of mass action C. Pythagoras theorem D. Quate law

THEORY

1. List five examples of energy conversions and their converters in each case.
2. Explain  the term exercise physiology.

READING ASSIGNMENT

Precious seed BASIC SCIENCE FOR JUNIOR SECONDARY SCHOOLS BOOK 2 PAGE 121

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