AIIMS2018Physics-Laws of Motion

AIIMS 2018 Physics Tension in a Lift MCQ Question

Type: MCQ-numerical-Medium-Class 11

A person of mass 60 kg is inside a lift of mass 940 kg and presses the button on control panel. The lift starts moving upwards with an acceleration 1 m/s². If g = 10 m/s², the tension in the supporting cable is

A

8600 N

B

9680 N

C

11000 N

D

1200 N

Correct Answer

Option C

Detailed Explanation

To find the tension (T) in the supporting cable when the lift accelerates upwards, we use Newton's second law. The total mass being accelerated is the sum of the person's mass (60 kg) and the lift's mass (940 kg), giving a total mass of 1000 kg. The net force required for the upward acceleration (1 m/s²) is calculated as Fnet=(mtotal)(a)=1000kg×1m/s2=1000NF_{net} = (m_{total})(a) = 1000 \, \text{kg} \times 1 \, \text{m/s}² = 1000 \, \text{N}. Additionally, we must account for the gravitational force acting on the total mass, which is Fgravity=(mtotal)(g)=1000kg×10m/s2=10000NF_{gravity} = (m_{total})(g) = 1000 \, \text{kg} \times 10 \, \text{m/s}² = 10000 \, \text{N}. Therefore, the tension in the cable is T=Fgravity+Fnet=10000N+1000N=11000NT = F_{gravity} + F_{net} = 10000 \, \text{N} + 1000 \, \text{N} = 11000 \, \text{N}, making option C correct.

Options A (8600 N), B (9680 N), and D (1200 N) are incorrect as they do not account for the total gravitational force acting on both the lift and the person, nor do they correctly include

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