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.