NEET Practice Questions (MCQs) with Answers & Solutions

The process described involves two phases: first, the time taken to react (reaction time) during which the vehicle continues to move (reaction distance), and second, the time taken for the vehicle to stop after the brakes are applied (braking distance or stopping distance). The NCERT mentions 'Reaction time is the time a person takes to observe, think and act. For example, if a person is driving and suddenly a boy appears on the road, then the time elapsed before he slams the brakes of the car is the reaction time.' This implies motion during reaction time. 'stopping distance...is an important factor for road safety and depends on the initial velocity (v0) and the braking capacity'.

From the formula $d_s = -v_0^2 / (2a)$, we can see that stopping distance ($d_s$) is inversely proportional to the magnitude of deceleration ($|a|$). A larger deceleration means the vehicle can slow down and stop more quickly, hence covering a shorter distance. The negative sign for 'a' implies deceleration, so we consider its magnitude.

As per the NCERT example, the reaction time ($t_r$) is calculated using the formula $d = \frac{1}{2} g t_r^2$. Rearranging for $t_r$: $t_r = \sqrt{\frac{2d}{g}}$. Given $d = 21.0 \text{ cm} = 0.21 \text{ m}$ and $g = 9.8 \text{ m/s}^2$. So, $t_r = \sqrt{\frac{2 \times 0.21}{9.8}} = \sqrt{\frac{0.42}{9.8}} = \sqrt{0.0428...} \approx 0.207 \text{ s}$. Rounding to two significant figures, $t_r \approx 0.21 \text{ s}$.

The NCERT definition of reaction time states: 'Reaction time is the time a person takes to observe, think and act.' It also mentions that 'Reaction time depends on complexity of the situation and on an individual,' disproving the first two options. The third option defines only the 'act' component, not the full process.

The NCERT text states: 'Urine formation involves three main processes, i.e., filtration, reabsorption and secretion. Filtration is a non-selective process performed by the glomerulus using the glomerular capillary blood pressure.'

The NCERT text mentions: 'Filtration is a non-selective process performed by the glomerulus using the glomerular capillary blood pressure.'

The NCERT text states: 'About 1200 ml of blood is filtered by the glomerulus per minute to form 125 ml of filtrate in the Bowman’s capsule per minute (GFR).'

The NCERT text states: 'The Bowman’s capsule encloses the glomerulus to form Malpighian or renal corpuscle.'

The NCERT text defines GFR as: 'The amount of the filtrate formed by the kidneys per minute is called glomerular filtration rate (GFR). GFR in a healthy individual is approximately 125 ml/minute, i.e., 180 litres per day!'

The NCERT text states: 'Glomerulus is a tuft of capillaries formed from afferent arterioles, fine branches of renal artery.'