Question Discussion & Solution

Stupid is the synonyms of Dumb.

Similarly,

Awful is the synonym of Horrible.

The pattern followed is:

Hence, the correct answer is "72".

The correct answer is Potato.

Modifications of Root

1. For storage of food
   • Roots are modified in some plants for storing reserve food materials.
   • These modified roots usually are swollen and assume different forms such as spindle-shaped, e.g., radish; top-shaped, e.g., beet, turnip; cone-like, e.g., carrot; indefinite shape, e.g., sweet potatoes.
   • Dahlia, Asparagus, Portulaca are some other examples of plants with modified roots for food storage.
2. Nodulated roots
   • The roots of pea and other leguminous plants have numerous swollen nodules on fine branches of roots.
   • These nodules are formed due to the symbiotic association of Rhizobium (bacterium) that live inside the root cortical cells of the roots.
   • They fix nitrogen and an active nodule is pink in colour.
3. For mechanical support
   • Roots are modified to provide mechanical support as seen in a banyan tree which has roots growing vertically/obliquely downwards (prop roots); sugarcane/maize in which roots arise from the nodes in the cluster at the base of the stem (stilt roots) and betel/black pepper in which nodes and internodes bear roots which help in climbing.
4. For gaseous exchange
   • Pneumatophores or breathing roots are found in plants growing in mangroves or swamps with saline water for exchange of gases.
   • They are erect peg-like structures with numerous pores through which air circulates e.g., Rhizophora mangle.

• Modifications of Stem

1. For storage of food
   • Stems get modified into underground structures for storage of food as seen in potato (tuber), ginger (rhizome), garlic (bulb), yam (corm).
   • Presence of an eye (node) in potato, distinct nodes with internodes and scaly leaves in ginger/yam, a cluster of roots at the base of the reduced stem in garlic/ onion, all indicate that these underground plant parts are modified stem.
2. For vegetative propagation
   • Plants besides reproducing sexually also propagate through vegetative parts.
   • For this purpose, stems may be modified into a runner (Cyanodon dactylon, Oxalis). Runners are slender prostrate branches arising from axillary buds;
   • stolon (e.g., mint, strawberry) which is a slender lateral branch arising from the base of the stem grows upward and then down to develop new daughter plants;
   • offset having a single long horizontal internode growing up to some distance and producing a tuft of leaves above and a cluster of roots below at the apex (Eichornia, Pistia) and
   • sucker, which arises from the underground part of the stem, grow obliquely and gives rise to a new shoot. (Chrysanthemum, Banana, Pineapple).
3. For protection
   • Some modified stem provides protection as thorns which are hard, pointed structures each representing a branch that arises from the axil of a leaf.
   • Thorns are found in plants like Duranta, Pomegranate, Acacia, Ber, Prosopis, Bougainvillea, Citrus, etc.
4. For support
   • Tendrils are modifications of the stem to provide support to plants, e.g., Vitis, passionflower, Bignonia etc.
5. For photosynthesis
   • Stems are also modified into Phylloclade, to facilitate photosynthesis.
   • Phylloclades are flattened/cylindrical stem or branches of unlimited growth (Cactus).

The correct answer is Its momentum is doubled.

Key Points

• Momentum is a vector quantity; it has both magnitude and direction.
• Isaac Newton’s second law of motion states that the time rate of change of momentum is equal to the force acting on the particle.
• Momentum can be calculated by multiplying the mass of an object by its forward velocity. (mv = kg*m/s).
• Mass and velocity are both directly proportional to the Momentum.
  • If you increase either mass or velocity, the Momentum of the object increases proportionally.
  • If you double the mass or velocity, you double the Momentum.
  • If you halve the mass or velocity, you half the Momentum.
• Newton's laws of motion-
  • ​Newton’s first law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by force. This postulate is known as the law of inertia.
  • Newton’s second law is a quantitative description of the changes that a force can produce in a body's motion. It states that the time rate of change of a body's momentum is equal in both magnitude and direction to the force imposed on it. The momentum of a body is equal to the product of its mass and its velocity.
  • Newton’s third law states that when two bodies interact, they apply forces to one another equal in magnitude and opposite in direction. The third law is also known as the law of action and reaction. This law is important in analyzing static equilibrium problems, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion.

Important Points

• Acceleration, the rate at which velocity changes with time in terms of both speed and direction. A point or an object moving in a straight line is accelerated if it speeds up or slows down. Motion on a circle is accelerated even if the speed is constant because the direction is continually changing.
• Kinetic energy, a form of energy that an object or a particle has because of its motion. If work, which transfers energy, is done on an object by applying a net force, the object speeds up and gains kinetic energy. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass.
• Potential energy, stored energy that depends upon the relative position of various parts of a system. Spring has more potential energy when it is compressed than stretched. A steel ball has more potential energy raised above the ground than it has after falling to Earth.

CONCEPT:

• Power: The rate of work done is called power.
  • It is denoted by P.
  • Mathematically it is written as

\(Power\;\left( P \right) = \frac{{\;W}}{{t}}\)

CALCULATION:

Given - mass of 1^st person (m₁) = 80 kg, mass of 2^nd person (m2) = 60 kg, time (t₁) = 12 sec, and time (t2) = 11 sec​

• The power to take an object to a certain height in 12 sec by 1^st person is 

\(\Rightarrow P_1 = \frac{mgh}{t}=\frac{80gh}{12}\)       ----(1)

• The power to take an object to a certain height in 11 sec by 2^nd person is 

\(\Rightarrow P_1 = \frac{mgh}{t}=\frac{60gh}{11}\)       ----(2)

On dividing equations 1 and 2, we get

\(\Rightarrow \frac{P_1}{P_2} =\frac{\frac{80gh}{12}}{\frac{60gh}{11}}=\frac{11}{9}\)