Physics in Depth

Physics Practice Set II A hose A ball A of mass 0.2 kg, moving with a velocity of 8 m/s, collides directly with a ball B of mass 0.3 kg at rest. Calculate their common velocity if both balls move together. If A had rebounded with a velocity of 3 m/s in the opposite direction after collision, what should be the new velocity of B? Solution : For ball 'A', mass , \(m_1\) = 0.2 kg velocity before collision, \(u_1\) = 8 m/s For ball 'B', mass, \(m_2\) = 0.3 kg velocity before collision, \(u_2\) = 0 Let \(v\) be the common velocity of both balls after collision. From the conservation of linear momentum, \[\begin{align} m_1u_1+m_2u_2&=(m_1+m_2)v\\ 0.2 \times 8 + 0 & = (0.2 + 0.3) v\\ v& = \frac {1.6}{0.5}\\ \therefore v&= 3.2 \hspace{0.1cm} \text{m/s} \end{align}\] If A had rebounded with a velocity of 3 m/s , then, velocity of A

Physics Practice Set I Can a quantity have unit but no dimensions? If yes give an example. Solution : Yes, a quantity can have unit but still be dimensionless. For example, the unit of angle is radian which has no dimension. Can the resultant of three forces be zero? Explain. Solution : Force is a vector quantity and has specific rules of addition and subtraction. The resultant of three forces can be zero if both of the following conditions are satisfied: The magnitude of resultant of two forces is exactly equal to the magnitude of the third force. The direction of the resultant of these two forces is exactly opposite to the direction of third force. Is there any point for projectile at which its acceleration is perpendicular to its velocity? Solution : Consider a projectile fired at an angle with the horizontal or the levelled ground. When the projectile reaches th

Group A Solution Why is the conductivity of an electrolyte very low as compared to a metal at room temperature? Solution: Conductivity depends on both the concentration (i.e. number density) and drift velocity of charge carriers. The concentration of ions (charge carriers in electrolytes) is very low compared to the concentration of free electrons (charge carriers in metals) and even the ions drift slowly due to their heavier mass. Hence, conductivity of an electrolyte is very low compared to metal at room temperature. What are the advantages of A.C. over D.C.? Solution: A.C. refers to the alternating current and D.C. refers to the direct current. Both are advantageous in their own way and have limitations too. However, in the modern era, use of A.C. has increased drastically due to many reasons. Some of the main advantages of A.C. over D.C. are as follows: A.C. is more economic in use than D.C. due to its lesser generation, transmi

  NEB Class 12 model question for Physics National Examination Board has published the model questions for grade 12 examination going to be held from Mangshir 9, 2077. Though, it was initially scheduled to be held from Baisakh 8, 2077, NEB postponed the examination for Manghsir 9 with all health safety measures as per safety guideliness setup by Government of Nepal. Here, I have attached the model question for Physics published by NEB.

Second law of thermodynamics Consider a container with rigid walls partitioned into two separate walls with a valve such that a gas is put in one part and other part is created a vacuum. Now, the valve is opened and the gas eventually occupies both the parts of the container. Is the reverse possible? i.e., put the gas in both the parts of the container with the valve open. Is it possible for the gas go into one part and evacuate the other part all by itself? Ofcourse , NOT . It does not even violate the first law of thermodynamics but still the reverse process does not occur. This is explained by the another law called the second law of thermodynamics . Second law of thermodynamics can mainly be stated by following two statements: Kelvin's statement : It is impossible to get a continuous supply of work from a body by cooling it to a temperature lower than that of its surroundings. Clausius statement : It is impossible for a self acting machine unaided

First law of thermodynamics Thermodynamic system is any macroscopic system (i.e., the system involving extremely large number of particles ). Thermodynamic systems may be closed (exchange of energy(heat or work) between system and the surroundings but not the matter) , open (exchange of energy and matter between the system and the surroundings) and isolated (no exchange of energy and matter between the system and the surroundings). Thermodynamic parameters are measurable quantities associated with the system, such as the pressure P , the volume V and the temperature T . A thermodynamic state is the set of thermodynamic parameters that are required for the description of the system. For e.g., ( P , V , T ) is the thermodynamic state that describes the thermodynamic system having pressure P , the volume V and the temperature T . A thermodynamic system is said to be in thermodynamic equilibrium when the thermodynamic state