CBSE ADDA

Q. If you want to lift the water to damp against the force of gravity what is the energy used by motor.given that Mass=20Kg ; Height=20m;Gravity=9.8m/s; Time=20min Ans: Work done by the motor against the gravity, W = mgh = 20×9.8×20 = 3920 J Power delivered by the motor = W/t =3920/(20×60) = 3.27 J/s Q. when a ball is lifted to a height of height h when it is drooped just before touching the ground, what would the kinetic energy acting on the ball. Ans: mgh According to the conservation of energy Potential energy is converted into kinetic energy just above the ground. Just before touching the ground the kinetic energy of the body is equal to mgh Q. what are the conditions where the work can be zero? Ans: Work done is said to be zero if the force is acting at right angles to the displacement of the body or when there is no displacement of the body. Example: Work done by the force of gravity on box lying on a roof of a bus moving with a constant velocity on a straight

1. Excretion is the removal of metabolic waste products called --------------- (Excreta) 2. The mammalian RBCs are without -------  (nucleus) 3. The heart is covered by a protective double walled sac called -----------filled with ------- ( pericardium , pericardial fluid.) 4. The heart is made up of special type of muscles, called ------------  (cardiac muscles) 5. The separation wall between right and left side of heart is called ------------ (septum) 6. ------------ regulate the flow of blood unidirectional from right auricle to right ventricle and not backwards.  (Valves) 7. Expanded condition of right and left ventricles when full of blood is called ----------------. (Diastole) 8 The state of contraction of of right and left ventricles is called -------- (systole) 9. ---------------- are thinnest blood vessel (Capillaries) 10. Except the -------------- veins all other veins carry deoxygenated blood. ( pulmonary) 11. ----------- are

Transportation and Excretion 7 th Biology William Harvey was an English physician was the first to give the details of blood circulation, the properties of blood and the pumping of blood by the heart. William Harvey was an English physician was the first to give the details of blood circulation, the properties of blood and the pumping of blood by the heart. 1. Q. Explain form and function of urinary system in man? Urinary system consists of Kidney, The ureters, the urinary bladder and the urethra.  The Functions of the Urinary System: The kidneys regulate blood volume and composition, help to regulate blood pressure and pH, participate in red blood cell production and synthesis of vitamin D, and excrete waste products and foreign substances. The Nephron tubule is the functional unit of the kidney . The ureters transport urine from the kidneys to the urinary bladder. The urinary bladder stores urine and expels urine into the urethra, The urethra discharges ur

8 th   Mensuration CBSE Enrichment questions 1. A rectangular tank can hold 650 litres of milk . if it is 130cm long & 250cm wide , find the height of the tank. Solution:   Volume of   rectangular tank   = 650 litres = 650 × 1000 cm   3   = 650000 cm   3 We know that  Volume of a cuboid = l × b × h 650000 = 130 × 250 × h ⇒   h = (650000)/( 130 × 250 )= 20 cm Therefore, height of the tank = 20 cm 2. a hall is of length 16m , breadth 14m & height 5m . Calculate the no: of persons that can be accommodated in the hall , assuming 3.5m 3   of air is required for each person. Solution:   ∴ Volume of the hall = length × breadth × height                                                     = 16 × 14 × 5                                                       = 1120 m 3 Volume occupied my 1 man = 3.5 m 3 3.5 m 3    of air   occupied my 1 man 1120 m 3    of air   occupied my   (   1/3.5)x   1120= 320   man Therefore, n