CBSE Class 9 - Science - Chapter 10 - Floatation & Archimedes’ Principle

Floatation & Archimedes’ Principle

Italian Stamp in honour of Archimedes
credits: St. Andrews Univ

Chapter Notes, NCERT Q & A and Numerical Problems

1. The force acting per unit area of the object is known as pressure.

 The SI unit of Pressure is N/m² or Pascal (Pa)

2. Density or Mass density is the ratio of mass per unit volume.

The SI unit of density is kg/m³
A density of an object is a key factor that decides whether it’ll float or sink in a liquid.

Q3: The weight of a man is 690N which contains 5.3 x 10^-3 m³ of blood.
Find (a) blood's weight. Take density of blood is 1060 kg/m³
        (b) express it as a percentage of body weight.

Answer: (a) Since  m = ρ x V
and W = mg
∴ W = (ρV)g = 1060 x 5.3 x 10^-3  x 9.80
⇒ W = 54N

CBSE - Class 10 - Biology - Chapter 15 - Our Environment

Chapter: Our Environment

Q1: Define Ecology

Answer: Ecology is a scientific study of the interactions between organisms and the environment. Ecology integrates all areas of biological research and  informs environmental decision.

Q2: What is the scope of Ecology Research?

Answer: Ecology study can be broadly classified as:
           a. Organismal Ecology
           b. Population Ecology
           c. Community Ecology
           d. Ecosystem Ecology
           e. Landscape Ecology
           f. Global Ecology

In nutshell, Ecology study advocates protection of nature and the environment.

Q3: Define Ecosystem.

Answer: An environment comprises of all living (biotic) and non-living (abiotic) things that occur naturally on the Earth or any of its region. All these living organisms interact with each other and their growth, reproduction and other activities are affected by the abiotic components of ecosystem.

Q4: Is garden an example of Ecosystem?

Answer: Yes. In an garden, all biotic components (e.g. plants, trees, animals like rats, frogs, birds, insects etc.) interact with each other and with abiotic components (garden soil, water etc.) for their growth and reproduction and other activities. Thus garden forms an ecosystem.

Q5: Give examples of natural ecosystems.

Answer: Forests, ponds, lakes, sea, oceans, coral reefs, rivers etc.

Q6: Give examples of human made (artificial )ecosystems.

Answer: Gardens, Crop-fields etc.

CBSE Class9-Science 11 (Work, Power Energy) MCQ

Work, Power Energy

MCQs

Q1: An example of Kinetic energy would be:
a. a moving car
b. a charge particle in an electric field.
c. a stretched rubber band just released.
d. all of the above.

Q2: Newton-meter is the SI unit of 
a. acceleration
b. work
c. power
d. force

Q3: Which of the following is/are example(s) of Potential Energy
a. A moving car.
b. A battery
c. A book resting on the table
d. both b and c

NTSE SAT Quiz-7 (History)

Test your knowledge about Indian History. answer these simple 7 questions. Enter your name and email-id, and click on 'Start' button to start quiz. If you like it, do send me your comments, I will prepare more MCQs on suggested topics.

NTSE (SAT History) » Quiz maker software

Tips and Checklist before appearing for NTSE Stage-1 Examination

This Sunday, November 20, 2011 is all set for NTSE Stage 1 examination. You may get details about the NTSE examination from NCERT website.

Following are important Tips and  checklist before going for the test.

1. Photocopy your hall ticket for future reference. The original Hall Ticket is taken by the invigilators at the examination hall. Do not forget to bring your hall ticket other wise you will not be allowed to enter the hall.

2. Reach the examination center at least 45 minutes to 1 hour earlier.  Sometimes hustle and bustle occurs for finding the seats.

3. Most of the times, the examination venues chosen for NTSE examination are Government Schools. It might happen there are not proper desks and candidates have to sit on mats. You should bring your own card boards to write properly.

4. Carry 3-4 HB sharpened pencils, eraser, a sharpener and a pen. Don't forget to wear your wrist watch. Calculators in any form are not allowed.

Why do people, having skin problems, are advised not to wear violet or red clothes?

Q: Why do people, having skin problems, are advised not to wear violet clothes?

Answer: Violet  rays coming from the sun carry high energy. Once such radiation falls on the thin skin, it reacts immediately. It may aggravates the skin problem or might produce other side effects.

NTSE MAT Quiz-1 (Series completion)

Complete the following series:

1.  6,12,21,___,48,66
 (a) 33      (b) 38       (c) 40       (d) 45

2.  125,80,45,20,___
 (a)  5        (b)    8     (c) 10        (d)12

3.  22,24,28,___,52,84

 (a)  30        (b)   36      (c)    42     (d) 46

4. 1,3,3,7,6,13,10,___,15,31


(a)  25        (b)   27      (c)    21     (d) 30

5. 3,1,7,3,13,7,21,15,31,31,___,63,57


(a)    39      (b) 41        (c)  38       (d) 43

Hindi Synonyms Quiz ( पर्यायवाची प्रश्नोत्तरी)

पर्यायवाची प्रश्नोत्तरी                                                     

१.अद्भुत 
(क) अजीब ,अनोखा
(ख)  अनुपम,विचित्र
(ग) आश्चर्यजनक ,विलक्षण
(घ) अपूर्व,अलौकिक

२.अंक 
(क) संख्या,गोद
(ख) चिन्ह,लेख
(ग) धब्बा,पाप
(घ) गोद,निशान

३.अंचल 
(क) आँचल,छोर
(ख) सीमान्त,प्रान्त
(ग) तट,किनारा
(घ) सीमा ,भूभाग

NTSE SAT Quiz-7 (Maths)

Q1: The sides of a right triangle are a, a+d, a+2d with a and d both positive. What is the value of ratio a:d ?
(a) 1: 3
(b) 1:4
(c) 2:1
(d) 3:1

Q2: In a group of cows and hens, the number of legs was 14 more than twice the number of heads. the number of cows is:
(a) 5
(b) 7
(c) 12
(d) 14

Q3: Each edge of cube is increased by 50%. The percent increase in surface area of the cube will be:
(a) 50
(b) 125
(c) 150
(d) 300

CBSE Class 9 - Chapter 11- Physics - Work And Energy (Q and A)

Work & Energy (Q & A)

Q1: A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the
force. Let us take it that the force acts on the object through the displacement. What
is the work done in this case?

Answer:  Let F be the force acting on the object displacing it by distance S, in the same direction of the force.
∴  F = 7N   and S = 8m
Work done (W) = Force (F) × Displacement (S)

 = 7 x 8 = 56 Joules

Q2(NCERT): When do we say that work is done?

Answer: Work is said to be done when the following conditions are met:
        (i) a force acts on the body.
       (ii) A displacment of the body occurs by virtue of applied force in the direction of applied force.

Q3(NCERT): Define 1 J of work.

Answer: 1 J is the amount of work done by a force of 1 N on an object that displaces it through a distance of 1 m in the direction of the applied force.

Q4: Is Work a scalar or vector quantity?

Answer: Although work is product of two vectors, it is a scalar quantity.