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NEET PHYSICSLAWS OF MOTIONMedium

Question

If a person with a spring balance and a body hanging from it goes up and up in an aeroplane, then the reading of the weight of the body as indicated by the spring balance will:

A

Go on increasing

B

Go on decreasing

C

First increase and then decrease

D

Remain the same

Step-by-Step Solution

  1. Initial Ascent (Acceleration Phase): When the aeroplane takes off and ascends, it accelerates vertically upwards with acceleration aa. According to Newton's Second Law, the force (tension TT in the spring balance) is given by Tmg=maT - mg = ma, so T=m(g+a)T = m(g + a). This apparent weight is greater than the actual weight (mgmg). Thus, the reading increases initially.
  2. High Altitude Phase (Variation of g): As the aeroplane reaches higher altitudes ('goes up and up'), the acceleration due to gravity (gg) decreases with height (hh) according to the relation gh=gR2(R+h)2g_h = g \frac{R^2}{(R+h)^2}. As gg decreases, the weight (mgmg') decreases.
  3. Cruising Phase: Additionally, when the plane reaches a steady cruising altitude, the vertical acceleration aa becomes zero, returning the apparent weight to mgmg' (which is already lower than ground mgmg due to altitude).
  4. Conclusion: Consequently, the reading first increases due to the initial upward acceleration and subsequently decreases due to the decrease in gravity at high altitudes. (Reference: NCERT Class 11, Physics Part I, Chapter 5: Laws of Motion [Apparent Weight]; Chapter 8: Gravitation [Variation of g]).

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from LAWS OF MOTION. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSLAWS OF MOTIONpersonspringbalancehangingaeroplane

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