1. An athlete runs a certain rest before taking a long jump. Why?
An athlete runs a certain distance to accelerate himself and gain enough momentum so that he can jump through the maximum possible length. 2. Springs are provided in car seats. Why? The springs in the car seats absorb shock (sudden jumps) due to the roughness of the road. Thus, making the ride more comfortable. 3. A gun of mass 1500 kg fires a shell of mass 15kg with velocity 150 m/s. calculate velocity of recoil of the gun. Before firing, total momentum of the gun and shell is = 0 (they were all at rest) After firing, the momentum of the shell = 15 X 150 = 2250 Ns The momentum of the gun is = 1500v Ns By conservation of momentum, Total momentum before firing = Total momentum after firing => 0 = 2250 + 1500v => v = -2250/1500 = -1.5 m/s The negative sign implies the recoil velocity of the gun is opposite to the velocity of the shell. 4. Why cricketer pulls his hands backwards while catching the ball Ans: cricketer pulls his hands backwards while catching the ball. When he does so, momentum of the ball reduces slowly, and time t required for this increases. As per F =DP/t , as t increase, magnitude of F decreases. As a result cricketer can catch the ball, easily, without any injury. 5. Why A karate player in order to break a brick, hits it quickly. Ans: A karate player in order to break a brick, hitsit quickly, so in a short time there is a large change in momentum and as per F =change in p/t as large force acts on the brick and it breaks. 6. What is impulse of Force? Ans: Product of force and the time period for which force is acting is called impulse of force. If, on an object, Force F acts for time t. Then Impulse of force = force x time I = F x t= change in p Like force, impulse of force is also a vector quantity. Direction of impulse of force is same as the direction of force. Unit of impulse of force is kg m/s or Ns. For more Question click Here
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1. An object of mass 2 kg is sliding with a constant velocity of 4 m/ s on a frictionless horizontal table. The force required to keep the object moving with the same velocity is
(a) 32 N (b) 0 N (c) 2 N (d) 8 N (b] 2. Rocket works on the principle of conservation of (a) mass (b) energy (c) momentum (d) velocity [c] 3. A car is moving at 45 km/hr.A constant force acts on the car for 10 sc .So that it's velocity becomes 63 km/hr .The distance travelled by car during this interval of 10 sec is : a) 100 m b) 150 m c) 200 m d) 50 m [b] What is the definition of balanced and unbalanced force? When two equal forces acting on an object in opposite directions called balanced force. When something does not move the forces are balanced, e.g. Gravity pulls a table down but that table is pushed up by the floor or the ground it stands on so doesn’t’ move. An Unbalanced force is needed for something to change movement or change direction, e.g. aseesaw moving up and down because the forces are not equal. Net force: - The sum of all the forces acting on a body is known as net force. Difference between Balanced force and unbalanced force. Balanced force:- If net force on a body is zero it is called balanced force. Balanced forces do not cause a change in motion. They are equal in magnitude and opposite in direction. Therefore, the resultant of these forces will be zero. Example: Two persons pushing a box with the same force in opposite directions. Unbalanced forces:- If net force on a body is non-zero it is called unbalanced force. Forces whose resultant is not equal to zero are called unbalanced forces. For example: An arm wrestling competition among a strong person and a weak one. The resultant force will be in the direction of the force applied by the strong person. What Is Inertia By Newton's law we know that ,a body at rest will remain at rest and a body in motion will continue in a straight line unless it is compelled by an external force.This tendency of a body is called inertia.So we can say that 'Inertia is that property of a body due to which it resists a change in its state of rest or of uniform motion.' When the brakes are applied to the bike the back seater moves forward why? Read more » you may also like IX Force and laws of motion solved questions: NCERT / CBSE Textbook Exercise Questions Solved For full study package free visit 1. Fill in the blanks:- (a) New cells are formed from pre-existing cells. (b) Movement of water molecules from their higher concentration to their lower concentration through a semi- permeable membrane is called Osmosis. (c) The functional components of cell are plasma membrane, cytoplasm & nucleus. (d) Protoplasm has two parts- cytoplasm & nucleoplasm. (e) Nucleus, mitochondria & plastids have their own DNA & ribosomes. (f) The shrinkage or contraction of the contents of the cell away from the cell wall is known as plasmolysis. (g) The process by which Amoeba can engulf a food particle is endocytosis. (h) Biogenesis is the manufacture of lipids required for making cell membrane. (i) A cell that lacks nuclear membrane is called a prokaryotic cell & the nuclear region is called nucleoid. (j) Movement of materials in & out of the cell takes place by diffusion & osmosis. 2. What is the advantage of multicellularity over unicellularity? Ans- Division of labour. 3. What are the chromosomes made up of? Ans- DNA & proteins 4. A cell placed in a solution swells up. What kind of solution is it? Why does it happen? Ans- It is a hypotonic sol ution & water enters the cell by endosmosis causing the cell to swell up. 5. Why are lysosomes known as “suicidal bags”? Ans- They secrete powerful digestive enzymes to digest the worn out and damaged cell organelles as well as the cell itself when it loses its functional ability. 6.Why is the nucleus so significant in a cell? Ans- Nucleus has the following important functions- (i) It controls all cell activities (ii) It contains hereditary material that transmits hereditary information from one generation to the next (iii) It helps in cell division 7. Differentiate between plant and animal cells. 1. PLANT CELL 1- Surrounded by two membranes- cell wall & cell membrane. 2- Possess three types of plastids chloroplasts, chromoplasts, leucoplasts. 3- Do not possess lysosomes. 4- Nucleus is towards the periphery. 5- Centrioles are absent ANIMAL CELL 1- Surrounded only by cell / plasma membrane. 2-Do not possess plastids. 3-Possess lysosomes4-Nucleus is in the center .. 5-Centrioles present & help in cell division. 8. Give the major functions of the following cell organelles- (a) Endoplasmic reticulum RER-- Synthesis of proteins as it has ribosomes attached to it SER- Synthesis of lipids required for making cell membrane (b) Golgi apparatus-----------Storage & packaging of various products. (c) Mitochondria------Production of ATP(Adenosine Triphosphate) which is a source of energy. (d) Ribosomes ---Protein synthesis (e) Golgi ApparatusStorage & packaging of various products. f) LysosomesDigestion of worn out & damaged organelles You may also like :
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Q. What is distillation? Ans: Distillation is a method of separating mixtures based on differences in their boiling points. The compound which have higher boiling point will distillate later while the compound which have lowest boiling point will distillate out first. Q. How is blood a heterogeneous substance? Ans: Blood is a heterogeneous mixture because it a mixture of plasma, blood cells, glucose, proteins, mineral ions, hormones and many different salts dissolved in it. Thus the dispersed phase and dispersed medium are in different physical state and hence a heterogeneous mixture Q. Calculate the mass of sodium sulphate required to prepare its 20% ( mass percent ) solution in 100g of water? Ans: Mass % of Sodium sulphate in the solution = 20% If the total mass of the solution = 100g Then mass of sodium sulphate = (20/100)x100 = 20 g Mass of water = 100-20 = 80 g. Q. Arun has prepared 0.01% ( by mass ) solution of sodium chloride in water, calculate the composition of soltution. How do you do it ? Ans: Mass % of solute = 0.01 % of NaCl in water Mass % of solute = [Mass of solute in grams / Mass of solution in grams] x 100. Let us suppose that mass of the solution is 100 g. Therefore mass of NaCl = 0.01 g Mass of water = 100-0.01 = 99.99 g. Q. How to separate components from mixture containing sulphur, charcol , pottasium nitrate? Ans: The mixture containing sulphur, charcoal and potassium nitrate can be separated by following technique: A. Add water to the mixture. Potassium nitrate will dissolve in water. Filter the solution. B. Filterate is solution of potassium nitrate and residue contains sulphur and charcoal. C. Evaporate the filterate, water will vapourize leaving behind potassium nitrate. D. To the residue containing sulphur and charcoal add carbon disulphide, this will dissolve sulphur. E. Filter this solution. F. The filtrate will contain sulphur dissolved in carbon disulphide and residue will be charcoal. G. Evaporate the filtrate, to obtain crystals of Sulphur. Q. Acetone evaporates in normal room temp. Why do we have to heat it to its boiling point? Ans: At room temperature the rate of evaporation of acetone is slow, to speed up the process to evaporate all the acetone in the mixture, we supply heat. You may also try: Q1. Define force and its SI unit?
Q 2. Distinguish between balanced and unbalanced force? Q3. State three laws of motion? Q 4. What is inertia? Is inertia vector quantity. Justify? Q5. What is impulse? Prove that Impulse is equal to change in momentum? Q. 6. Define momentum and Prove that F = ma Q 7. Is it possible that a body keeps on moving with uniform velocity with? If yes give reason also name scientist who explained this statement? Q 8. Why a person sitting in bus fall forward when moving bus suddenly stops? Q9. Why people sitting in bus fall backward when bus suddenly starts? Q10. Why dust fall on beating carpet with stick? Q11. Why leaves fall when we are shacking branch of tree? Q12. Why an athlete runs certain distance before taking long jump? Q13. When bus takes u turn, passengers sitting inside thrown a side. Why? Q14. Explain why it is difficult for a fireman to hold a hose, which ejects large amount of water at a high velocity. Q15. How a karate player can break a pile of tiles with a single blow of his hand? Q.16. Why does a bullet when fired against a glass window pane make a hole in it, and the glass pane will smash it? Q.17. Why is it advised to tie a rope on the luggage while you travel by the bus? Q18.Why vehicles are provided with shocker? Q19. Why does a bicycle begin to slow down when we stop pedaling? Q20. State and verify the law of conservation of momentum? Q21. When we hit at the bottom of the pile of carom coins, other coins fall vertically on the carom board why? Q22. Two balls A and B of masses 'm' and '2 m' are in motion with velocities '2 v' and 'v' respectively. Compare (i) their inertia (ii) their momentum and (iii) the force needed to stop them in the same time Q 23. A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40,000 N and the track offers a friction force of 5,000 N then calculate: (a) the net accelerating force (b) the acceleration of the train (c)the force of the wagon 1 on rest of the wagons. Q 24.According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the road side, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move. Q25.A machine gun can fire 50 g bullets with a velocity of 150 m/s. A 60 kg stone is moving towards the machine gun velocity of 10 m/s. How many bullets must be fired from the gun to just stop the stone in its tracks? Class IX Science SA-1 Quick Links IX Motion and rest IX Force and Law of motion IX Gravitation IX Matter in our surrounding IX Is matter around us pure IX Biology Term-1 |
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