Q1-Week 2 (SCIENCE 8)- Work, Power, and Energy

Q1-Week 2 (SCIENCE 8)- Work, Power, and Energy

by Teacher Gerazel

​WORK, POWER, AND ENERGY

• ​Work is useful in defining energy.

• ​Without energy and power, you cannot create work.

Fill in the Blanks

​When is Work Done?

​Work is done whenever a force produces movement.

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​Work is done to transform energy from one form to another.

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For work to be done the force exerted should be parallel to the displacement.

Multiple Select

Identify who is showing "work".

(Multiple answers)

• A teacher applies force to a wall and becomes exhausted.

• A father carrying the baby across the room.

• A book falls off a table and free fall to the ground.

• A mother lifting up the baby from the crib.

A teacher applies force to a wall and becomes exhausted.

This is not an example of work. The wall is not displaced. A force must cause a displacement in order for work to be done.

​WORK IS DONE WHEN THE FORCE APPLIED IS PARALLEL TO THE DISPLACEMENT

The father carrying a baby acros sthe room​

​No part of the force is parallel to the displacement.

​A book falls off a table and free fall to the ground.

​This is an example of work. There is a force (gravity), that acts on the book which causes it to be displaced in a downward direction

​A mother lifting up the baby from the crib.

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As she lifts the baby the force exerted on the baby is parallel to the displacement.

Work is a product of the magnitude of displacement multiplied by the component of the force parallel to the displacement.

Formula:​

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​UNIT FOR WORK (W) is JOULES (J) =

Open Ended

When do we say that work is done on an object?

Multiple Select

Click on the choices if work is done on the following situation.

CHOOSE AS MANY ANSWERS THAT MAY APPLY WORK

• A boy running across the playground

• A mother dancing with the baby in her arms

• A basket being lifted

Multiple Choice

Click on the choices if work is done on the following situation.

CHOOSE AS MANY ANSWERS THAY MAY APPLY WORK

• A person in an ascending elevator

• A stone whirled around a horizontal circle

• A big box dragged across the floor.

Work Done at an Angle​

REVIEW YOUR GEOMETRY​

Multiple Choice

Analyze the picture. What angle is used in the picture?

• SOH

  $$\sin\theta=\frac{opp}{hyp}$$  

• CAH

  $$\cos\ \theta=\frac{adj}{hyp}$$  

• TOA

  $$\tan\ \theta=\frac{opp}{adj}$$  

​How is Power Developed?

Power is the rate of doing work.

​FORMULA USED

​Where:

​W = work

​F= force parallel to the displacement

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SAMPLE PROBLEM 1 & 2​

Multiple Choice

Which do you think arrives in the classroom first?

• RUNNING MAN

• WALKING MAN

• NONE 

​POWER

​FORMULA:

​S.I. Unit of is (J/s or watts (W)

​CONVERSION OF UNITS

​1 joule/second (J/s) = 1 watt (W)

​1000 watts = 1 kilowatt (kW)

​1 horsepower (hp) =746 watt

​ANSWER PRACTICE MATH (PAGES 25 & 28)

​POWER

​Is the RATE of doing work

​KINETIC ENERGY

​is the energy possessed by bodies in motion

​POTENTIAL ENERGY

​Stored energy.

​GRAVITATIONAL POTENTIAL ENERGY

​The higher an object, the higher the gravitational potential energy.

​KINETIC ENERGY

​Depends on the mass and speed of the body.

Since speed ( is doubled it takes,

​its KE is increased by a factor of 4

​SAMPLE PROBLEM 1

​POTENTIAL ENERGY

​An object in an elevated position is said to have gravitational potential energy

​The height lifted against gravity, not the distance moved.

​SAMPLE PROBLEM 2

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