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#height calculation

6 public questions tagged with this topic.

At what height above Earth’s surface is g reduced to 5.88m/s2? (g0\=9.8m/s2,RE\=6.4×106m)

g(h) = g0(1+h/RE)2. 5.88 = 9.8(1+h/RE)2. (1+h/RE)2 = 1.667. 1+h/RE = 1.667≈1.291. h/RE = 0.291. h = 0.291×6.4×106≈1.86×106m. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.9 × 10⁶ m. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

At what height above Earth’s surface is g reduced to 7.84m/s2? (g0\=9.8m/s2,RE\=6.4×106m)

g(h) = g0(1+h/RE)2. 7.84 = 9.8(1+h/RE)2. (1+h/RE)2 = 1.25. 1+h/RE = 1.25≈1.118. h/RE = 0.118. h = 0.118×6.4×106≈7.55×105m. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 7.6 × 10⁵ m. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

A body experiences g\=7.35m/s2 at a certain height above Earth. What is the height? (g0\=9.8m/s2,RE\=6.4×106m)

g(h) = g0(1+h/RE)2. 7.35 = 9.8(1+h/RE)2. (1+h/RE)2 = 9.87.35≈1.333. 1+h/RE = 1.333≈1.154. h/RE = 0.154. h = 0.154×6.4×106≈9.86×105m. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 9.9 × 10⁵ m. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

A ball is thrown upwards at 45m/s from a 30m tower. What is the time taken to reach a point 15m above the ground? (Take

Displacement y=−15m, −15=45t−5t2⇒5t2−45t−15=0⇒t2−9t−3=0. As per NCERT Chapter 3, equations v=u+at, s=ut+½at², v²=u²+2as describe uniformly accelerated motion. Applying correct signs and units gives 9 s as the result, so option A is correct.

Ref: NCERT Class 11 Physics > Chapter 3: Motion in a Straight Line > Topic: Equations of Motion and Problem Solving

A stone falls from a height and covers 58.8m in the last 1.2s of its fall. What is the total height? (Take g\=9.8m/s2)

Total time = t, last 1.2 s: 58.8=9.8t−4.9(t−1.2)2. As per NCERT Chapter 3, equations v=u+at, s=ut+½at², v²=u²+2as describe uniformly accelerated motion. Applying correct signs and units gives 210 m as the result, so option A is correct.

Ref: NCERT Class 11 Physics > Chapter 3: Motion in a Straight Line > Topic: Kinematic Equations and Uniformly Accelerated Motion