Q217 / 240 · KCET 2026 · Physics
A man weighs $80$ kg. He stands on a weighing scale in a lift which is moving upwards with a uniform acceleration of $6 \text{ m/s}^2$. What would be his weight in kg? ($g = 10 \text{ m/s}^2$)
- AZero
- B$48$ kg
- C$120$ kg
- Correct answerD$128$ kg
Solution
Mass of the man, $m = 80 \text{ kg}$
Acceleration of the lift, $a = 6 \text{ m/s}^2$ upwards
The weighing scale measures the normal reaction $N$. The equation of motion for the man is:
$N - mg = ma$
$N = m(g + a)$
Substituting the given values:
$N = 80(10 + 6) = 1280 \text{ N}$
The reading of the weighing scale in kg is:
$\dfrac{N}{g} = \dfrac{1280}{10} = 128 \text{ kg}$
Answer: $128$ kg
Acceleration of the lift, $a = 6 \text{ m/s}^2$ upwards
The weighing scale measures the normal reaction $N$. The equation of motion for the man is:
$N - mg = ma$
$N = m(g + a)$
Substituting the given values:
$N = 80(10 + 6) = 1280 \text{ N}$
The reading of the weighing scale in kg is:
$\dfrac{N}{g} = \dfrac{1280}{10} = 128 \text{ kg}$
Answer: $128$ kg
Hence, the correct answer is option: 'D'.