# Test Revision Notes

Motion and Measurement of Displacements

Ancient measurement methods: –

• Handspan
• Length of a foot
• Width of a finger
• Distance of a step
• Cubit: The length from the elbow to the fingertips
• Yard: The distance between the end of the outstretched arm and chin

Standard units of measurement: –

• The comparison of an unknown quantity with some known quantity resulting into a fixed quantity is called a
• Scientists all over the world have accepted a set of standard units of measurement known as the International System of Units (SI units).
• The SI unit of length is a metre (m).
• Each metre (m) is divided into 100 equal divisions, called centimetre (cm). Each centimetre has ten equal divisions, called millimetre (mm).
1. 1 m = 100 cm
2. 1 cm = 10 mm
• Large distances is measured using a larger unit of length called kilometre (km).
1. 1 km = 1000 m

Measurement of length

• Metre scales, measuring tapes, and metre rods are some of the devices that are commonly used to measure length in daily life.
• The choice of measuring device is important when measuring length, as one cannot measure the girth of a tree directly using a metre scale.
• In taking a measurement of a length, the following points must be taken into consideration:
• The scale must be placed in contact with the object along its length.
• In cases where the zero mark of the scale is not visible or broken, use any other full mark of the scale and subtract the reading of this mark from the reading at the other end.
• The eye must be exactly in front of the point where the measurement is to be taken.
• The length of a curved line cannot be measured directly using a metre scale. A thread can be used to measure the length of a curved line along with the metre scale.

Motion and its types

• An object is said to be at rest if it does not change its position with time.
• An object is said to be in motion if it changes position with time.

• Adolescence – period of life when the body undergoes certain changes leading to reproductive maturity.
• starts around the age of 11 and ends up to 18 or 19 years of age which also referred to as the teenager
• the reproductive organs begin to develop and become functional, which is known as reproductive health.

• Puberty – human body undergoing several changes during adolescence. during which a child develops into an adult.
• Puberty begins a year or two earlier in girls than in boys.

Changes at Puberty

• growth of facial and body hair.
• increased secretion of sweat and sebaceous glands
• widening of chest and shoulders in boys, and enlargement of breasts in girls.
• the changes in voice and fat distribution.
• boys experience puberty a year or two before girls.
• the individual also undergoes mental, intellectual, and emotional maturation.

Role of Hormones during Puberty

Role of Hormones in Initiating Reproductive Function

Reproductive phase of life in humans

Menstrual Cycle

• reproductive process unique to females.
• begins at puberty and is marked by the onset of menarche.
• With changes in the ovaries, the uterus undergoes cyclic changes preparing the body for a potential pregnancy.
• An ovum is released from the ovary, and the uterus develops a thick, spongy inner lining.
• If the egg is fertilised, pregnancy occurs; otherwise, the released egg and the thickened lining of the uterus are shed off, resulting in bleeding known as menstruation.
• Menstrual cycles usually cease between the ages of 45 and 52, which is known as menopause.
• This is the reproductive age of a female when she can bear children.

Sex determination

• Zygote is the instruction which are thread like structures for determining the sex of a baby and is called
• Sex is determined by one of the 23 pairs of chromosomes found in the nuclei of human cells. Out of 23 pairs, one pair called the sex chromosome.
• Females have two X chromosomes, while males have one X and one Y chromosome.
• The gametes which will eventually fuse, contain only one set of chromosomes.
• The ovum always has an X chromosome. When a sperm containing X chromosome fuses with an egg, it develops into a female child.
• When a sperm containing Y chromosome fuses with an egg, it develops into a male child.

Reproductive Health

• Maintaining personal hygiene is important during teenage years, as increased levels of sweat can cause body odour, as well as acne.
• To prevent bacterial and fungal infections, we should clean and wash all parts of the body on a daily basis.
• Eating a balanced diet is essential for teenagers as it provides the body with all of the necessary nutrients to fuel its growth.
• A balanced meal includes proteins, carbohydrates, fats, and vitamins in the right proportions.
• Regular physical exercise like walking, playing, or practising yoga as it maintains healthy body and mind.
• Drugs are highly addictive and can cause severe, long-term harm to the body.
• It is important for teenagers to stay away from drugs.
• HIV can spread through the sharing of syringes used to inject drugs.
• Can be transmitted to an infant from an infected mother through her milk or to another person through sexual contact.
• people who are addicted to drugs are at a higher risk of contracting HIV.
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