Key Notes chapter Motion

 1. For motion in a straight line, position to the right of the origin is taken as positive and to the left as negative.

2. A body in straight line motion can have the line of path as vertical, horizontal or slanted.

3. Path length is defined as the total length of the path traversed by an object.

 4. Distance: Total path length covered during a given time interval.

5. Displacement: Shortest straight line distance between the initial and final position.

6. Path length is greater or equal to the magnitude of the displacement between the same points. 

7. An object is said to be in uniform motion in a straight line if its displacement is equal in equal intervals of time. Otherwise the motion is said to be non-uniform.

8. Average speed: Total distance traveled divided by the total time taken.

 9. Average velocity: Total displacement divided by total time taken.

10. The average speed of an object is greater or equal to the magnitude of the average velocity over a given time interval.

11. Slope of the x-t graph gives the velocity at a given instant.

12. Position time graph of a body in non uniform motion is curved.

13. Velocity time graph of a body in non uniform accelerated motion is curved.

14. Slope of v-t graph gives the acceleration at that instant.

15. The area between the v-t graph and the time axis gives the displacement

16. The steepness of the slope of position vs. time graph tells us the magnitude of the velocity & its sign indicates the direction of the velocity.

17. If the tangent to the position vs. time curve slopes upward to the right on the graph, the velocity is positive.

18. If the tangent to the position time graph slopes downward to the right, the velocity is negative.

19. For one-dimensional motion, the slope of the velocity vs. time graph at a time gives the acceleration of the object at that time.

Syllabus Of Class IX Science SA I

Month	Chapter Name	No. of Periods
April	Motion     Matter in our Surroundings	8 to 10 Periods             5 to 7  Periods
May	Cell – Basic Unit of life	10 to 12 Periods
June	Force and laws of motion    Is Matter around us pure	8 to 10 Periods             5 to 7 Periods
July	Gravitation (Half) Tissue	4 to 6 Periods             8 to 10 Periods
August -September	Revision and Test Series	Note: Every 2nd and 4th Sunday will be Test after chapter completion.

Astigmatism

Astigmatism is a common eye condition that's easily corrected by eyeglasses, contact lenses, or surgery.

Astigmatism is caused by an eye that is not completely round. This is one type of refractive error. Astigmatism occurs in nearly everybody to some degree. For vision problems due to astigmatism, glasses, contact lenses, and even vision correction procedures are all possible treatment options.

A person's eye is naturally shaped like a sphere. Under normal circumstances, when light enters the eye, it refracts, or bends, evenly, creating a clear view of the object. However, the eye of a person with astigmatism is shaped more like a football or the back of a spoon. For this person, when light enters the eye it is refracted more in one direction than the other, allowing only part of the object to be in focus at one time. Objects at any distance can appear blurry and wavy.

                                                                   What Causes Astigmatism?

Astigmatism is a natural and commonly occurring cause of blurred or distorted vision. The exact cause in not known.

What Are the Symptoms of Astigmatism?

People with undetected astigmatism often have blurred vision which can be associated with fatigue and eyestrain. While these symptoms may not necessarily be the result of astigmatism, you should schedule an eye exam if you are experiencing one or more symptoms.

How Is Astigmatism Diagnosed?

Your eye doctor can diagnose astigmatism with a thorough eye exam. Astigmatism may occur with other vision problems such as nearsightedness and farsightedness. Because astigmatism may increase slowly, you should visit your eye doctor whenever you notice changes in your vision. 

How Is Astigmatism Treated?

Almost all degrees of astigmatism can be corrected with properly prescribed eyeglasses or contact lenses. For a person with only a slight degree of astigmatism, corrective lenses may not be needed at all, as long as other conditions, such as nearsightedness or farsightedness, are not present. If the astigmatism is moderate to high, however, corrective lenses are probably needed.

• Corrective lenses (eyeglasses or contact lenses). For astigmatism, special soft contact lenses called toric lenses are prescribed. Soft toric lenses have greater light bending power in one direction than the other. Another option, particularly for higher amounts of astigmatism, is a gas permeable rigid contact lens. After performing various tests, your eye doctor will determine the ideal prescription for your astigmatism.
• Refractive surgery. Another method for correcting astigmatism is by changing the shape of the cornea through refractive or laser eye surgery. While there is more than one type of refractive surgery, specific treatments are recommended on an individual basis.

Refractive surgeries require healthy eyes that are free from retinal problems, corneal scars, and any eye disease. As technology progresses, it is becoming more and more important that you explore all options and possibilities before deciding which refractive surgery and treatment is right for you.