Write answers within the space provided under the question :
Name of the type of force acting :
A straw rubbed with paper attracts another straw

According to Hooke's law, within the elastic limit stress/strain = constant. This constant depends on the type of strain or the type of force acting. Tensile stress might result in compressional or elongative strain, however, a tangential stress can only cause a shearing strain. After crossing the elastic limit, the material undergoes elongation and beyond a stage beaks. All modulus of elasticity are basically constants for the materials under stress. If stress/strain is x in elastic region and y in the region of yield, then

When the powder of a common metal is heated in an open china dish, colour turns black. However, when hydrogen gas is passed over the hot black substance formed, it regains its original colour. Based on this information, answer the following questions : (i) What type of chemical reaction takes place in each of the two given steps ? (ii) Name the metal initially taken in the powder form. Write balanced chemical equations for both these reactions.

Two types to aquatic organisms in a lake show specific growth patterns as shown below, in a brief period of time. The lake is adjacent to an agricultural land extensively with fertilizers. Answer the question based on the facts given above : (i) Name the organisms depicting the patterns A and B. (ii) State the reason for the growth pattern seen in A. (iii) Write the effects of the growth patterns seen above.

Identify a, b and c in the schematic diagram of an antibody given here and answer the question : (i) Write the chemical nature of a antibody. (ii) Name the cells that produce antibodies in humans. (iii) Mention the type of immune response provided by an antibody.