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A lift is going up. The total mass of the lift and the passenger is 1500 kg. The variation in the speed of the lift is as given in the graph. The height to which the lift takes the passenger is

A

3.6 meters

B

8 meters

C

1.8 meters

D

36 meters

Step-by-Step Solution

To find the height to which the lift takes the passenger, we need to calculate the displacement. The displacement is given by the area under the speed-time (v-t) graph .

Based on the standard graph associated with this specific problem (often found in competitive exams like NEET/AIPMT 2013), the motion corresponds to a trapezium with the following phases:

  1. Acceleration: From t=0t = 0 to t=2t = 2 s, speed increases from 0 to 3.6 m/s.
  2. Constant Speed: From t=2t = 2 to t=10t = 10 s, speed remains constant at 3.6 m/s.
  3. Deceleration: From t=10t = 10 to t=12t = 12 s, speed decreases from 3.6 m/s to 0.

Calculation: Height=Area under the curve=Area of Trapezium\text{Height} = \text{Area under the curve} = \text{Area of Trapezium} Area=12×(Sum of parallel sides)×(Height)\text{Area} = \frac{1}{2} \times (\text{Sum of parallel sides}) \times (\text{Height}) Sum of parallel sides = Total time + Time of constant motion = 12 s+(102) s=12+8=20 s12 \text{ s} + (10 - 2) \text{ s} = 12 + 8 = 20 \text{ s}. Height of graph = Maximum speed = 3.6 m/s3.6 \text{ m/s}.

Height=12×(20)×3.6\text{Height} = \frac{1}{2} \times (20) \times 3.6 Height=10×3.6=36 meters\text{Height} = 10 \times 3.6 = 36 \text{ meters}

The mass of the lift (1500 kg) is not required for calculating the displacement from the v-t graph.

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