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Smita studied about the Modern Periodic Table. She placed hydrogen, lithium, sodium, and calcium in the same group in the periodic table. However, her teacher told her that she has placed one element incorrectly in the periodic table.(Atomic numbers of H, Li, Na, and Ca are 1, 3, 11, and 20 respectively) Which element has been placed incorrectly by Smita?

Elements containing same number of valence electrons are present in the same group of the modern periodic table. The number of valence electrons... View Article

How would these advantages differ from the advantages of using a long-term perspective in managing our resources?

If resources are used in accordance with short term aims, the present generation will be able to utilize the resources properly for growth and... View Article

Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.

Inside the loop = Pierce inside the table Outside the loop = Appear to emerge out from the table For downward direction of current flowing in the... View Article

What are the different ways in which individuals with a particular trait may increase in a population?

An individual trait may increase in a population in the following ways The trait is beneficial to the population: if a trait is beneficial to... View Article

In the case of real gases, the equation of state, PV = RT (where P, V and T are respectively the pressure, volume and absolute temperature), is strictly satisfied only if corrections are applied to the measured pressure P and the measured volume V. When does the corrections for P and V arise?

In kinetic theory of gases it is assumed that there is no force between molecules But there is actually intermolecular attraction which reduces... View Article

Give two reasons to justify: a) Water at room temperature is a liquid. b) An iron almirah is a solid at room temperature.

Water at room temperature is liquid due to the presence of hydrogen bond. These bonds hold water molecules together for small fractions of a... View Article

Which hormone causes dilation of blood vessels, increased oxygen consumption and glucogenesis? a)Adrenaline b)Serotonin c)Insulin d)Thyroid

Adrenaline is secreted by the adrenal medulla. It mainly acts on smooth muscles, cardiac muscles, blood vessels, skeletal muscles and fat cells.... View Article

A scooter waiting on a signal has its mirror vibrating violently. Why?

This is because of resonance. When a body is subjected to forced vibration with a frequency which equal to or an integral multiple of the natural... View Article

Name the physical quantity which we get from a S-t graph.

Speed-Time Graphs look much like Distance-Time graph. Time is plotted on the X-axis. Speed or velocity is plotted on the Y-axis A straight... View Article

In the following example, try to identify the number of times the velocity of the ball changes: “A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team”. Also identify the agent supplying the force in each case.

The velocity of football changes four times. First, when a football player kicks to another player, second when that player kicks the football to... View Article

Why is it difficult to hold a school bag having a strap made of a thin and strong string?

It is difficult to hold a school bag having a thin strap because the pressure on the shoulders is quite large. This is because the pressure is... View Article

What is an induced movement?

Induced movement or induced motion is an illusion of visual perception in which a stationary or a moving object appears to move or to move... View Article

Which of the following molecules show the presence of intramolecular hydrogen bonding? (a) Cellulose (b) HCN (c) Concentrated Acetic Acid (d) H₂O₂

Option (a) Cellulose Cellulose shows the presence of intra molecule hydrogen bonding in them. This is due to the fact that the Glucose monomers... View Article

Newton’s first law of motion is also known as the law of__________

Answer: Newton's first law of motion is also known as the law of inertia. Newton's first law of motion states that an object in rest or in... View Article

Two identical metallic spheres, having unequal opposite charges are placed at a distance of 0.90 m apart. After bringing them in contact with each other, they again placed at the same distance apart. Now the force of repulsion between them is 0.025 N. Calculate the final charge on each of them.

Let the initial charges be q1 and q2 respectively. After they come in contact, the charges are rearranged such that they acquire same charge.... View Article

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

The ray of light bends towards the normal. The light ray bends towards the normal. When a light ray enters from an optically rarer medium... View Article

Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?

Answer: Given parameters Potential difference (V) = 220 V Power of lamp 1 (P1) = 100 W Power of lamp 2 (P2) = 60 W Both the bulbs are... View Article

A copper ball of mass 100 gm is at a temperature T. It is dropped in a copper calorimeter of mass 100 gm, filled with 170 gm of water at room temperature. Subsequently, the temperature of the system is found to be 75°C. T is given by : (Given : room temperature = 30° C, specific heat of copper = 0.1 cal/gm°C (1) 1250°C (2) 825°C (3) 800°C (4) 885° C

A copper ball of mass 100 gm is at a temperature T. It is dropped in a copper calorimeter of mass 100 gm, filled with 170 gm of water at room... View Article

Certain force acting on 20 kg mass changes its velocity from 5 m/s to 2 m/s. Calculate the work done by the force

Answer: Work is said to be done when a force applied to an object moves that object. Work done is generally referred to in relation to the force... View Article

What are the changes seen in girls at the time of puberty?

Puberty is when a child's body begins to develop and change as they become an adult. At the time of puberty, secondary sexual characters develop,... View Article

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