Clarification Clarification Factors to Win the Race Amount

Clarification

Clarification

Factors to Win the Race • Amount of Force by the legs The greater the better. • Amount of time the force is exerted The lesser the better.

Walking a distance of 1 km Which can tire you easily? Sprinting a distance of 1 km

Walking a distance of 1 km WHY? Sprinting a distance of 1 km

Question Which of the following requires more work in lifting a box of books? • lifting this box onto a shelf in 2 s • lifting each book so that it takes 20 min to put them all on the shelf

Lifting the box Which is more tiresome? Lifting each book

Walking up a flight of stairs Which is more tiresome? Running up a flight of stairs

Quiz No. 6

Instructions • • Use a piece of size 4. Identification “Is Work Done? ” Problem-solving

Identification Complete the equation.

Number 1 W = ___ x ___

Number 2 P = ___ / ___

Number 3 P = ___ x ___ (regular)

Number 3 P = (___ x ___) ___ (semi-honors)

Is there work done? Respond to the question by writing YES or NO.

Number 4 Is work done on the notebook?

Number 5 Is work done on the notebook?

Number 6 Is work done on the notebook?

Number 7 Is work done on the notebook?

True or False Write True if the statement is ALWAYS true. Otherwise, write False.

Number 8 Work is done every time an object is acted by a force and is displaced.

Number 9 A 10 -W bulb does twice amount of work compared to a 5 -W bulb.

Number 10 Work is done on an object experiencing uniform circular motion.

Problem solving Show your complete solution. Enclose your answer in a box or an ellipse.

Problem Solving How much work is done on a 75 -N bowling ball when you carry it horizontally across a 10 -m-wide room?

Objective • Define energy; • Derive and interpret the work-energy theorem; and • Define kinetic energy and its components.

Simple Review • What is work? • What is the unit of work? • When does WORK become ZERO even when FORCE and DISPLACEMENT are NOT ZERO?

• What is ENERGY? The ability to do WORK. • What does this definition mean in relation to the concept of WORK? We need ENERGY in order to do WORK. We spend ENERGY when we do WORK.

Am I doing work ON THE ERASER?

Am I spending ENERGY?

Am I doing work ON THE BOARD?

Am I spending ENERGY?

Am I doing work ON THE BODY?

Am I spending ENERGY?

Where does the ENERGY go?

• What is ENERGY? The ability to do WORK. • What does this definition mean in relation to the concept of WORK? We need ENERGY in order to do WORK. We spend ENERGY when we do WORK.

Relationship of Work and Energy Work changes the energy level of an object.

Work – Energy Theorem W = ΔKE

Work – Energy Theorem KE = ½ 2 mv Kinetic energy is the energy resulting from motion.

Work – Energy Theorem W = ΔPE

Gravitational Potential Energy PE = mgh Potential energy is the stored energy resulting from a relative height.

Work – Energy Theorem W = ΔE

Work – Energy Theorem E = KE + PE

Seatwork Use size 1. Use GRESA. Answer numbers 1, 2 and 3 of page 261 of Glencoe textbook.

Problem for the Giants A sled is being pulled across a horizontal patch of snow. Friction is negligible. The pulling force points in the same direction as the sled’s displacement, which is along the +x axis. As a result, the kinetic energy of the sled increases by 38%. By what percentage would the sled’s kinetic energy have increased if this force had pointed 62 o above the +x axis?

The End

Energy Source What is our source of energy? Food is a source of energy. Energy can be stored. Energy can be transferred.

Trace that ENERGY.

Seatwork • Use size 2. • Use GRESA. • Answer numbers 1, 2, and 3 of page 287.

Quiz 5 – Identification 1. State the equation to compute for work with no reference to energy. 2. At what angle relative to displacement should force be applied in order to do the maximum work? 3. At what angle would work be zero even how great is the magnitude of force applied? 4. State the most concise form of the workenergy theorem?

Quiz 5 - Identification 4. State the equation to compute for work with no reference to energy. 5. State the equation to solve for the kinetic energy.

Quiz 5 – True or False 6. There is a net work done to a body that is moving. 7. In order to change the kinetic energy of a body, it is necessary that net force is exerted on that body. 8. The sun is applying net work on Earth. 9. The body applied with a net work is an accelerating body.

Quiz 5 – Problem Solving If a net work of 45. 0 Joules is applied to a resting bayong filled with goods (about a total mass of 10. 0 kg), at what speed will it move?

Questions • • Is force applied on the rubber band? Is the rubber band displaced? Is there work done on the rubber band? Is energy spent

Learning from a Bird

Trace that ENERGY.

Conservation of Energy

• Mechanical energy is the sum of the kinetic energy and the gravitational potential energy. E = KE + GPE

Conservation of Mechanical Energy When the MECHANICAL ENERGY of the system is constant before and after any event that happens, it is said to be conserved.

Gravitational Potential Energy GPE = mgh It is the energy of a body by virtue of its position relative to a reference level.

Sample Problem • A 2. 0 -kg bag was raised from the floor to a height of 1. 0 meter. a. How much potential energy did the bag gain? b. How much work was done?

Making it complicated… Gravitational Potential Energy

Comparing GPE

Seatwork • Use Size 2. • Use GRESA. • Answer numbers 4, 5, and 6 of page 291.

Kinetic Energy And Gravitational Potential Energy In ONE SYSTEM

Zero potential energy position

Planetary Orbit Is there work done on a celestial body revolving around another body?

Energy Source Food is our source of ENERGY.

Homework • Read pp. 72 and 73 of the lab manual. • We will perform the activity on January 19, 2012. Prepare a ruler for the group. • Use letter size bond paper for your solutions and answers to the guide questions. • Deadline of submission is on January 25, 2012.

Number 1 Before the collision A +VA -VB B m. A = m B a. Illustrate your prediction. b. Are the initial speeds of both spheres equal? c. Before and after the collision, does the speed of sphere A remain constant? d. Is the final speed of sphere B equal to the initial speed of sphere A?

Number 2 Before the collision A -VB B m. A = m B a. Illustrate your prediction. b. Is the final speed of sphere A essentially equal to the initial speed of sphere B? c. What force should be neglected in order to maintain the speed of sphere B constant before the collision?

Number 3 Before the collision A -VB m. A = m B B Additional information: These are two metal spheres. Sphere A is magnetized. a. Illustrate your prediction. b. After the collision, is the speed of sphere B equal to sphere A? c. After the collision, what specifically happens to the magnitude of the speed of sphere A?

Remember? Two-Man Challenge

Homework Size 4 1. What is energy? 2. What is kinetic energy? 3. What is potential energy?

What do you need? • You need ENERGY in order to do WORK. • ENERGY is the ability to do work.

Let us do the TRACING. Pushing an object

Kinetic Energy is energy in motion.

Work-Energy Theorem W = ΔKE

Seatwork • Answer numbers 2 (a and b) and 3 (a, b, and c) of p. 261. • Use Size 2 • Use GRESA.

Quiz 3 1. Among the set-ups constructed during the great egg drop challenge, what were the two set-ups found to be the most effective in protecting the egg? Describe these set-ups in no more than 3 sentences. 2. What was the objective of the Last Dry Man Standing activity? State the objective in no more than 2 sentences

Quiz 3 3. Write the equation that states the impulsemomentum theorem that shows four distinct quantities. 4. How do you increase a body’s momentum?

Quiz 3 5. Based on the concept of impulse and momentum, choose a set-up that you mentioned in number 1. Explain in no more than 5 sentences why this set-up contributed to the safe landing of the egg. 6. Explain the technique used during the last dry man standing activity in no more than 5 sentences.

Quiz 3 F O R C E TIME 2 s Looking at these graphs, which of the two show a greater probability that an egg will break? Explain in no more than two sentences.

Work and Energy

Assignment • Visit WEEBLY. • Open the file named Take Me Home. • Deadline for submission is on January 17, 2012.

Example Before the collision A +VA B m. A = m B YOUR ANSWER After the collision B A m. A = m B +VB

Assignment Use letter size bond paper. IP Progress Report should be submitted on January 19, 2012. IP Final Paper – February 10, 2012

Two-Man Challenge

May I ask… 1. Of the two, in which round most probably made the volunteers tire out? 2. If we assume that in both rounds the speed of the mass was constant, what can we say about the force applied by the two? 3. If they applied that same amount of force, why did they get more tired in the second round?

For Your Information The energy required to chew a piece of banana is equal to the energy it has.

Seatwork • Answer numbers 2 (a and b) and 3 (a and b only of p. 261. • Use Size 2 • Use GRESA.