PHYSICS

Red rose appears red in white light because it reflects red colour and absorbs all the other colours of white light, but appears black in green colour because the only colour given to the flower is absorbed and nothing is reflected.

QUESTION: A vibrating tuning fork when held against the surface of a table produces a loud sound.  Give reason. ANSWER: A vibrating tuning fork forces the table top to vibrate. As the table top has large surface area, amplitude of vibration increases. 

QUESTION: What are superconductors? ANSWER: The materials whose resistivity is zero at very low temperature is called superconductors. Example: Mercury below 4K.

QUESTION: A satellite revolves around a planet in a circular orbit. What is the work done by the satellite at any instant? Answer: The work done is zero.  As the Centripetal force by the satellite is perpendicular to the displacement of the body.

QUESTION: Why is it  not advisable to use a piece of copper wire as fuse wire in an electric circuit.? ANSWER: Fuse wire should have low melting point and high resistivity but copper has high melting point and low resistivity. 

Question: Why does a stone lying in the sun get heated up much more than water lying for the same duration of time? Answer: The specific heat capacity of  stone is less than the that of  water.

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.