GR10 MECHANICAL ENERGY by Lizelle Swanepoel

ENERGY TRANSFORMATION

lizellexs — 2018-10-23 11:40:16 UTC

An energy transformation is the change of energy from one form to another. There are many different forms of energy such as:

kinetic energy = energy due to motion.
potential energy = energy due to position relative to a reference point.
electrical
thermal
nuclear
sound
chemical
light

This concept illustrates the Law of Conservation of Energy.
It states: Energy cannot be created or destoyed, but simply change from one form to another.

Therefore:
The total energy in the Universe never changes; it stays constant.

NOW: BUILD YOUR OWN NEWTON CRADLE TO INVESTIGATE THE TRANSFER OF ENERGY.
MATERIALS YOU ARE GIVEN:

5 Marbles
60 cm sticks
Sticky tape or glue
String

WHAT IS ENERGY?

lizellexs — 2018-10-23 11:41:55 UTC

DEFINITION:

Energy is the ability to do work.
Work is Energy transferred.
Also:

Work = The product of force and distance moved by an object.
(NOTE: The force is the component of the force in the direction of motion)

Equation for WORK: W = F x d

Therefor energy and work are interchangeable physical quantities.

E = W (Both have the unit of Joules)

When a system does work, its energy content will decrease.
Conversely, a system on which work is being done will have an increase in its energy content.

MECHANICAL ENERGY IN A WATERFALL

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Law of Conservation of mechanical energy

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The law states:
The total mechanical energy of a closed system remains constant.

For a pendulum swing:
Total E mech _top = Total E mech _bottommgh + 0 = 1/2mv²+ 0^{Check out Prof Walter Lewin below:}

The Double Pendulum

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Energy transfer & conservation of mechanical energy in a closed system

POTENTIAL ENERGY VS. KINETIC ENERGY

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Potential energy = Energy due to position relative to a reference point.

E_p = mgh

Gravitational Potential Energy = energy an object possesses due to its position relative to the ground.

Kinetic energy = Energy due to motion. E_k = ½ mv²
Mechanical energy = E_k + E_p

Potential energy example below:
Cupboard height = 2 m, Suitcase mass = 1 kg

PENDULUM PROBLEM

lizellexs — 2018-10-23 17:59:31 UTC

Do the following problem:
A metal ball of mass 0,2 kg is tied to a light string to make a pendulum. The ball is pulled to the side to a height (A), 0,1 m above the lowest point of the swing (B). Air friction and the mass of the string can be ignored. The ball is let go to swing freely.

Calculate the potential energy of the ball at point A.
Calculate the kinetic energy of the ball at point B.
What is the maximum velocity that the ball will reach during its motion?

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WORKED EXAMPLES: POTENTIAL ENERGY

1. A brick with a mass of 1kg is lifted to the top of a 4m 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)
E_P= mgh
= (1)(9,8)(4)
= 39,2 J

b)
E_P= mgh
= (1)(9,8)(0)
= 0 J

2. A netball player, who is 1,7 m tall, holds a 0,5 kg netball 0,5 m above her head and shoots for the goal net which is 2,5 m above the ground.
What is the gravitational potential energy of the ball:

when she is about to shoot it into the net?
when it gets right into the net?
when it lands on the ground after the goal is scored?

Solution:
1. Use the definition of gravitational potential energy to calculate the value for the ball when the girl shoots for goal
E_P=mgh
First we need to calculate h. The height of the ball above the ground when the girl shoots for goal is:
h = (1,7 + 0,5) = 2,2 m.

Now we can use this information in the equation for gravitational potential energy:
E_P= mgh
=(0,5)(9,8)(2,2)=10,78 J

2. Calculate the potential energy of the ball at the height of the net.
E_P=mgh
=(0,5)(9,8)(2,5)
=12,25 J

3. Calculate the potential energy of the ball on the ground
E_P=mgh
=(0,5)(9,8)(0)
= 0 J

Kinetic energy

lizellexs — 2018-10-23 18:17:21 UTC

WORKED EXAMPLES: KINETIC ENERGY

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1. A bullet, having a mass of 150 g, is shot with a muzzle velocity of 960 m·s⁻¹. Calculate its kinetic energy.

Solution:
E_K=1/2mv²= 1/2(0,150 )(960 )²= 69 120 J

Energy in a Nutshell

lizellexs — 2018-10-23 18:57:18 UTC

Roller Coaster Physics Calculations

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Mall of America "Spongebob Squarepants Plunge"

Roller Coaster Physics

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Energy transformations in a coaster ride:

ROLLER COASTER PROBLEM 1

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EXAM QUESTION continued...

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Mr Lambson is travelling down a hill in his Lamborghini when he suddenly runs out of fuel at point A. In the distance, over the next hill at B, Mr Lambson spots a fuel station at D. Use the ground as a reference point. Mr Lambson’s Lamborghini has a mass of 1600 kg, this includes the mass of Mr Lambson. Use the information and diagram above to answer the following questions. Ignore all friction.

1 State the Law of Conservation of Energy. (2)

2 State the Principle of Conservation of Mechanical

Energy. (2)

3 Calculate the total mechanical energy which Mr

Lambson’s Lamborghini possesses at A, assuming he

was rolling down the hill at 4 m.s^-1 when he ran out of

fuel. (3)

4 Calculate the potential energy of Mr Lambson’s

Lamborghini at B. (2)

5 Calculate the speed with which he will arrive at the fuel

station at D. (4)

TYPICAL EXAM QUESTION

lizellexs — 2018-10-24 09:58:32 UTC

Mechanical Energy = E_p + E_k(in a closed system)

Roller Coasters and Mechanical Energy

lizellexs — 2018-10-25 05:56:57 UTC

1817 - First roller coaster features cars that locked onto the track (Paris)

Build your own roller coaster!

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Wooden roller coasters: Shiver me timbers

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ROLLER COASTER LAB

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Purpose:

Your goal is to design and build the wildest roller coaster ride that will deliver a marble safely to the end. You must at least demonstrate three successful consecutive runs.

Criteria: Your roller coaster should have at least:

· 2 hills, 2 turns and 1 vertical loop (extra credit for extra loops, hills or turns)

Materials:

· 2 lengths of insulation tubing & marble

· Scissors & toothpicks

· Support material like wooden sticks or paper cups

· Stop watch (phone timer) & meter rule

Procedure:

Design a roller coaster and submit your design for approval before construction.
You need to do Potential energy and Kinetic energy calculations.
For this you need to measure the height of the roller coaster from where the marble starts to the base where the marble ends its trip.
You need to calculate the velocity of the marble as it finally rolls off into a cup.
The entire group must make the demonstration in front of the class and speak on their project for 3 minutes (about the history and physics of roller coasters, and a video your team’s experience in building it.)
Class will vote for best themed & decorated roller coaster (2-point bonus).

Calculations:

Mass of marble (kg) = m =
Track Height (m) = h =
Distance traveled_horizontal (m) = d_x =
Time t (s) =
Actual final velocity (m.s^-1) of marble v = d_x / t =
E_p (J) = mgh =
E_k (J) = ½mv² =
E _Lost (E_p– E_k) =
Theoretical final velocity of marble v = √(2gh) =

Conclusion:

When was the first roller coaster made?
Which is the world’s highest coaster?
What do you think happened to the energy lost during the marble ride?
What laws are being demonstrated during the marble ride?

Roller Coaster Project Rubric:
| Looking For… |

Way
Part Way
No Way

Scoring

| Presentation |

Well presented, covers the history, physics and team experience.
Reading from paper, some parts missing, lacking seriousness.
Missing major parts of presentation or making a joke of presentation.

Physics,History /2
Formal presentation /3

| Roller Coaster |

Has all the appropriate number of hills, loops and/or turns.
3 successful trials in a row | Missing some of the requisite features.
2 successful trials in a row | Missing loop. Trials mostly unsuccessful.

Features /3

| Workmanship & Theme |

Neat finish and well decorated. Has a well defined theme.
Wobbly. Theme is not apparent/ is silly/ is unappealing
No theme, Structure completely unstable

Workmanship /1 Theme /1

| Calculations |

All calculations done correctly.
Some calculations done wrong.
Large errors in calculations.

Calculations /5

| Conclusions |

All questions answered fully and correctly.
Some questions answered correctly or partial answers.
Answers wrong or show lack of understanding.

Conclusions /2

| Teamwork |

Team has worked well together to produce an effective and strong product, with equal distribution of tasks.
Some team members worked harder than others in completing the project.
Most of the work has been done by one or two people.

Effective Teamwork /3

TOTAL 20

WORK

lizellexs — 2018-10-26 04:59:59 UTC

Definition:
Work = The product of force acting on an object and the distance moved.
Formula:
W = F.d

Motion of the object must be in the direction of the component of the applied force acting on the object.

1885 - “CYCLONE”: 1st Powered Chainlift Roller Coaster; Coney Island, Brooklyn, New York

lizellexs — 2018-10-30 04:45:34 UTC

7 Forms of Energy - MRS CHEN (Acronym to memorize)

lizellexs — 2018-11-04 13:27:38 UTC

Mechanical energy = The Sum of kinetic energy and potential energy.
Kinetic energy is the energy due to an object’s motion.
Potential energy is the energy due to position relative to a reference point.

Radiant (Light) energy = Electromagnetic energy that travels through space as electrical and magnetic waves.
Other types of EM energy include radio waves, microwaves, X-rays and gamma rays.

Sound energy = a form of mechanical energy that starts with a vibration in matter. Sound waves can travel through matter; not through a vacuum (empty space).

Chemical energy = the energy stored in chemical bonds between atoms of a compound. If bonds are broken, energy is released and can be converted to other forms of energy.

Heat energy = the kinetic energy due to moving atoms in a substance.
All matter has thermal energy because atoms in a substance are constantly moving. An object with more mass has greater thermal energy than an object with less mass because it has more atoms.

Electrical energy = the energy of moving electrons.
Electrons flow through wires to create electric current.

Nuclear energy = energy stored in the nuclei of atoms due to the forces that hold the nucleus together.
The energy can be released by splitting nuclei apart and when unstable radioactive nuclei decay.

ANSWERS

lizellexs — 2019-06-02 13:13:40 UTC

EXERCISE 1

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EXERCISE 3

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EXERCISE 4

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EXERCISE 5

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EXERCISE 2

lizellexs — 2019-06-03 11:45:07 UTC

NOTES

lizellexs — 2020-05-03 22:07:13 UTC

lizellexs — 2020-05-06 15:47:51 UTC

EXERCISE 1

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Question 2 - SKETCH

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ROLLER COASTER WORKSHEET

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HOMEWORK: DO EXERCISE 5

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IDENTIFY THE LINK BETWEEN THE GIFS BELOW AND ENERGY CONVERSION

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TYPICAL EXAM QUESTION

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ANSWERS

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DEFINITIONS

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FORMULAE

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Alternative energy sources

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Graphs

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