PHYSICS

Why is echo not heard in our living rooms? To hear echo, the minimum distance between the source and the reflector must be 17m. When this distance is more than 17m, the reflected sound can be distinguished from the original. As the length of our rooms is less than 17m, we don't hear echo.

  SAMPLE PAPER FOR ICSE 2020 onwards, PHYSICS EXAM, 13 MARCH 2020  PHYSICS CLASS 10 FULL MARKS 80 GENERAL INSTRUCTIONS: 1. ANSWERS TO THIS QUESTION PAPER SHOULD BE WRITTEN IN ANSWER SHEETS PROVIDED SEPARATELY. 2. You ARE NOT ALLOWED TO WRITE IN FIRST 15 MINUTE. SPEND THIS TIME TO READ THE QUSETIONS THOROUGHLY. 3. THIS QUESTION PAPER IS DIVIDED INTO TWO SECTIONS: SECTIONS A AMD SECTION B. 4. SECTION A: ATTEMPT ALL QUESTIONS FROM THIS SECTION. 5. SECTION B : ATTEMPT ANY FOUR QUESTION. 6. MARKS ARE GIVEN IN BRACKETS [ ].  SECTION A (ATTEMPT ALL QUESTIONS )  QUESTION 1  a) Define centre of gravity and mark it for a triangular lamina. 2  b) A body of mass 500g is thrown vertically upwards with a velocity of 9.8 m/s, calculate the potential energy at the maximum height. (g=10m/s^2) 2 c) Name the class of lever for a short handle oar. Give one more example of this class of lever. 2  d) Screw Jack has a long handle bar. Give reason. 2 e) A...

What is elasticity? Elasticity is the property of a body by which the body regains it original configuration when the deforming force is released. Elasticity doesn't  mean the force to stretch  a body or how much we can stretch a body.

Speed of sound decreases with the fall in temperature as density of medium increases due to cooling.

Why does fog reduce visibility range? The fog particles scatter  light of all colour to the same extent as the size of particles  of fog is same or greater than that of  wavelength of light. As colours are scattered, the fog appears white and on the other hand the light from the other side does not reach the observer, so it reduces visibility.

ULTRASONIC WAVES What are the properties of ultrasonic waves? 1 They carry large amount of energy with them as they have high   frequency. 2. They travel in straight path.

The commercial unit of electric energy is kilowatt hour. We have  Energy =power ×time. Accordingly, Killowatt hour is the commercial unit as this unit is used to  measure electric energy and to prepare electricity bill.