Physics MCQs for NEET — Practice Questions with Answers

From Example 9.6: Force to be lifted ($F_2$) = mass $\times g = 1350 \text{ kg} \times 9.8 \text{ m/s}^2 = 13230 \text{ N}$. Radii are $r_1 = 5.0 \text{ cm}$ and $r_2 = 15 \text{ cm}$. We know $F_1/A_1 = F_2/A_2$, so $F_1 = F_2 (A_1/A_2) = F_2 (\pi r_1^2 / \pi r_2^2) = F_2 (r_1/r_2)^2$. $F_1 = 13230 \text{ N} \times (5/15)^2 = 13230 \text{ N} \times (1/3)^2 = 13230 \text{ N} \times (1/9) = 1470 \text{ N}$.

The text states, 'An important advantage of the system is that the pressure set up by pressing pedal is transmitted equally to all cylinders attached to the four wheels so that the braking effort is equal on all wheels.'

The explanation for Example 9.5 (b) explicitly states, 'Water is considered to be perfectly incompressible. Volume covered by the movement of smaller piston inwards is equal to volume moved outwards due to the larger piston.' This incompressibility is crucial for the efficient and direct transmission of pressure and displacement in hydraulic systems.

The text combines two aspects of Pascal's Law: 'The French scientist Blaise Pascal observed that the pressure in a fluid at rest is the same at all points if they are at the same height.' and 'whenever external pressure is applied on any part of a fluid contained in a vessel, it is transmitted undiminished and equally in all directions.'

The text states: 'It is necessarily the same in all. If we push the piston, the fluid level rises in all the tubes, again reaching the same level in each one of them.' This demonstrates the uniform transmission of pressure.

The text indicates the force is 'increased by a factor of $A_2/A_1$'. If $A_2 = 10 A_1$, then the factor is $10A_1/A_1 = 10$. So, the force is amplified 10 times.

The text states, 'The SI unit of pressure is N m$^{-2}$. It has been named as pascal (Pa)'. Also, its dimensions are '[ML$^{-1}$T$^{-2}$]'.

According to the provided text, 'Kirchhoff’s junction rule is based on conservation of charge and the outgoing currents add up and are equal to incoming current at a junction.' This highlights that the rule, stating the sum of currents entering a junction equals the sum of currents leaving it, is fundamentally about charge not accumulating at any point, hence conservation of charge.

The NCERT text explicitly states, '(b) Loop rule: The algebraic sum of changes in potential around any closed loop involving resistors and cells in the loop is zero'. This rule is a direct application of the conservation of energy, as potential difference is related to work done per unit charge.

The text explains: 'If ultimately I is determined to be positive, the actual current in the resistor is in the direction of the arrow. If I turns out to be negative, the current actually flows in a direction opposite to the arrow.'