1. (a) Why are wheels of vehicles made circular? (b) Name the type of microorganism that is smaller than bacteria. (c) What kind of force is an electrostatic force? (d) Name the force due to which every object falls on earth. (e) Why do pieces of luggage fitted with rollers? (f) Write the name of a bacterium that helps in the formation of curd. (g) What does yeast produce during respiration? (h) Who discovered the vaccine for small pox? (i) Name a microorganism which helps in nitrogen fixation. (j) Does the force of gravitation exist between two astronauts in space? 1x10=10 2. Define:- (Any 10) 2x10 =20 (a) Pressure (b) Force (c) Friction (d) Pathogen (e) Fermentation (f) Refrigeration (g) Vaccine (h) Decomposition (i)Communicable diseases (j) Antibodies (k) Magnetic and Electrostatic Force (l) Spring Balance. (m) Ohmic Heating 3. (a) Give two examples of each of the following types of microorganisms: (i) Algae (ii) Fungi (iii) Protozoa (iv) bacteria (v) Virus 2x5=10 4. (a) What is the role of bacteria in increasing the soil fertility? (b) Explain why antibiotics do not work against flu or any infection caused by viruses. (c) Mention any three ways through which pathogens are transmitted. (d) Explain how malaria is transmitted to humans. (e) What is the difference between Rhizobium and cyanobacteria in the way of fixing nitrogen for the plants? (f) Define Preservation. What are the various ways by which Preservation can be done,explain them. 3+3+3+3+2+6= 20 5. (a) Differentiate between (i)Contact and Non contact force. (ii) Mass and Weight. (iii) Push and Pull force (b) Seema got cough and cold badly. Her teacher asked her to take rest at home and use handkerchief while sneezing and coughing. She obeyed her teacher. (i) Why should we keep a handkerchief on nose and mouth while sneezing or coughing? (ii) What are the modes of transfer of diseases from infected to healthy person? (iii) Do you think Seema’s teacher decision was right? Why? (iv) What value of Seema is shown here? (c) Why it is easier to walk on soft sand if we have flat shoes rather than shoes with sharp heels (or pencil heels)? (d) Why do sea divers wear specially designed suits? (e) An archer shoots an arrow in the air horizontally. However, after moving some distance, the arrow falls to the ground. Name the initial force that sets the arrow in motion. Explain why the arrow ultimately falls down. (f)It is difficult to cut cloth using a pair of scissors with blunt blades. Explain. (g) How does the friction depend on the nature of the surface? 6+4+2+2+2+2+2=20 6. (a) The sliding friction is slightly smaller than the static friction. Explain why? (b) What are the causes of friction? Explain in detail. (c) On Lokesh’s birthday Shreya was given charge to amuse children with some little tricks. Shreya sticked balloons to the wall by just rubbing them in her clothes. She bent the water stream from a tap without touching it. She did so by bringing big balloon near to the flowing water. All children were very happy on seeing this little magic. Everybody praised Shreya. (i) How do balloons stick to walls? (ii) How Shreya bent the water stream by bringing a big balloon near it and without touching it? (d) Explain increasing and decreasing friction with suitable examples. (e) What do you mean by fluid friction? How can fluid friction be reduced? (f) Differentiate between (i) viruses and other microorganisms. (ii) Refrigeration and freezing. 2+5+2+4+3+4=20