Question:
A block of mass $m$ is suspended from the ceiling of a lift by an inextensible string. When the lift moves upward with an acceleration of $0.2\ \text{m s}^{-2}$, the tension is $80\ \text{N}$. Then the mass of the block is:
A block of mass $m$ is suspended from the ceiling of a lift by an inextensible string. When the lift moves upward with an acceleration of $0.2\ \text{m s}^{-2}$, the tension is $80\ \text{N}$. Then the mass of the block is:
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Apparent weight increases when a lift accelerates upwards ($T = m(g+a)$) and decreases when accelerating downwards ($T = m(g-a)$).
Updated On: May 10, 2026
- 1 kg
- 2 kg
- 8 kg
- 6 kg
- 4 kg
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The Correct Option is C
Solution and Explanation
Step 1: Concept
For an upward accelerating lift, the effective acceleration is $(g + a)$.
Step 2: Analysis
Tension $T = m(g + a)$. Given $T = 80\ N$, $a = 0.2\ ms^{-2}$, and assuming $g = 9.8\ ms^{-2}$.
Step 3: Calculation
$80 = m(9.8 + 0.2) = m(10)$. $m = 8\ kg$. Final Answer: (C)
For an upward accelerating lift, the effective acceleration is $(g + a)$.
Step 2: Analysis
Tension $T = m(g + a)$. Given $T = 80\ N$, $a = 0.2\ ms^{-2}$, and assuming $g = 9.8\ ms^{-2}$.
Step 3: Calculation
$80 = m(9.8 + 0.2) = m(10)$. $m = 8\ kg$. Final Answer: (C)
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