Potential Energy

Specifically, we're talking about gravitational potential energy

U7: Circles

Key Learning Points:

• The diameter of a circle is a straight line that starts from one point on the circle's perimeter, cutting through the centre of the circle and reaching the other point on the perimeter.
• The radius is a straight line drawn from the centre of the circle to the perimeter of the circle
• Thus 2 x radius = diameter
• Circumference is the perimeter of a circle
• Circumference = 'pi' x diameter or 'pi' x (2 x radius)
• 'pi' is generally taken to be 22/7 or 3.14 (questions will tell you which 'pi' to use)
• Area of a Circle = 'pi' x radius x radius

Generally, be careful with the units in this topic and if possible, try to use 'pi' as 22/7 as it is neater and does not contain decimals.

U6: Living Together

Key Learning Points:

• An organism is a living thing
• A population is a group of similar organisms that lives and reproduce together in the same place
• A habitat is the place where an organism or a population live, reproduce and finding food and shelter
• A community refers to many populations staying together in the same habitat
• All organisms in a community are interdependent, that is, they depend on each other for survival
• Be able to identify the types of organisms in the various habitats and communities

Examples of interdependence include:

• Green plants provide oxygen to animals during photosynthesis
• Animals and other plants provide carbon dioxide to the green plants during respiration
• Plants provide food and shelter to animals
• Animals' waste droppings fertilise the soil to help plants grow healthily

Terrariums:

• These are transparent enclosures where a mini-habitat is created for selected plants and animals of the same community
• The main purpose is to allow us to examine how each of the organisms affect/depend on each other for survival
• The observations are quire accurate as a terrarium roughly represents what that would take place in a real community / habitat

U5: Forces

Key Learning Points:

In this chapter you've learnt about the 4 types of forces.

(a) Frictional Forces (Or Friction)

• This force exists whenever 2 surfaces come into contact with each other
• Friction opposes (resist) motion and can cause wear and tear as well as producing heat (thereby causing overheating in machinery)
• However without it, we will not be able to walk properly or hold onto things
• We can never eliminate friction but we can reduce them
• Methods include adding lubricants (oil or grease), rollers and wheels, ball bearings or powder

(b) Gravitational Forces (Or Gravity)

• This is the pulling force of the Earth on all objects, which is measure by our weight
• It is different from mass, which is how much matter an object has
• Thus weight is NOT EQUAL to mass
• Gravity can work against us (e.g. climbing up stairs require more force to overcome gravity) or work in our favour (e.g. going down a slope)
• The gravity on the moon is 1/6 of the Earth's gravity. Thus we would weigh lighter on the moon than on the Earth

(c) Elastic Spring Force

• This force is present in springs or elastic bands
• When a pulling force is applied, the spring or elastic band is stretched. Upon releasing, the elastic spring force will cause the spring or elastic band to return to its original length
• The original length of the spring will be when there is no force/mass attached to it
• The extension of the spring is the result of a pulling force exerted on it

(d) Magnetic Force

• These are the forces of attraction and repulsion of a magnet
• Like poles of a magnet repels (pushes away) while unlike poles attract (pulls together)
• Magnetic materials can be attracted to a magnet, regardless of the poles
• E.g. Steel, Iron, Nickel, Cobalt, Manganese
• Magnetic material are not magnets. They need to be magnetised first either by the stroking method or the electrical method (resulting in an electromagnet)

U6: Time & Speed

Key Learning Points:

(A) Time

• Time is like the name given to any moment. E.g. 4.45p.m., 9.45a.m. etc
• It is fixed at any one time
• It can be written in the 12 hour clock or 24 hour clock
• In the 24 hour clock, 0000 is midnight, that is, the start of a new day. Thus in the 24 hour clock format, the time starts from 0000 to 2359.
• Duration is a measurement of how much time an activity takes. E.g. 1h, 5h 30 min, 45s, 38min etc
• NEVER add or subtract time and duration together as they are 2 different things! E.g. 1.45pm + 15min = 2pm WRONG!!>
• When dealing with time and duration, always draw a timeline to represent your workings

(B) Speed

• This means how fast an object or person is travelling at any unit (1) time
• Distance = Speed x Time
  
• Before you apply the formula, always make sure that the units of each of the above parts are 'talking' to each other.
• Meaning to say, if speed is given as km/h, make sure that the distance must be in 'km' and time in 'h'. (Do the necessary conversions e.g. 1km = 1000m and 1h = 60min)
• After solving for the answer, double check that your answer has the same unit as what the question wants. E.g. if the question wants you to give time in hours, make sure you convert your time from minutes to hour.
• When finding Average Speed, find the total distance and divide it by the total time taken.

This topic is not that difficult as long as you are very careful and alert with the units and the way you present your workings. All speed questions must have these 3 parts (Distance, Speed, and Time). All you need to do is to find them, make sure the units 'talk' to each other and apply the formula and some common sense into it.

Project Work Survey @ LEAD

6 Excellence!

Please log on to your LEAD to do a survey on the Product Package Project. It can be found in your Assignments section.

Homework / Tasks for T2W3

Tasks for this weekend of T2W3:

• Math Daily Problem Sums (Q35 to Q40)
• Math Practice 1 (Circles)
• English News Article Comprehension (2 pages)

Don't forget to study for the upcoming TESTS:

• Monday: Science Test (Living Together)
• Tuesday: Science Spelling (Living Together)
• Wednesday: English Spelling (Pg 1, 2, 3 and 5)

Announcements:

• No Health Ed and Assembly on Monday (7 Apr) - Convert to Maths Lessons
• No revision class on Monday (7 Apr)
• International Friendship Day Celebration on Thursday (10 Apr) - 1st 2 periods
• Sports Day on Friday (11 Apr)