An empty lift is positioned at the first floor of a building - Edexcel - A-Level Physics - Question 17 - 2023 - Paper 1

To find the total mass of the people in the lift, we must first identify the total tension when the lift has 10 people in it.

From the graph, we see that the tension is at a higher value (let’s assume it is around 19 kN when the lift starts moving upwards).

The total weight acting on the lift is: $ext{Weight}_{ ext{total}} = ext{Weight}_{ ext{lift}} + ext{Weight}_{ ext{people}}$

Converting the weights to Newtons, we have:

Therefore,

Now, using the gravitational force formula ($F = mg$) to find mass: $7,000 = m \times 9.81$ Thus, $m = \frac{7000}{9.81} \approx 712.5 ext{ kg}$

So, the total mass of the people in the lift is approximately 712.5 kg.

Between 5 seconds and 29 seconds, the lift exhibits a pattern of acceleration and deceleration based on the changes in tension indicated in the graph.

From 5 seconds, as the lift begins to move upwards, the tension in the cables increases, indicating that the lift is accelerating. This acceleration is necessary to overcome both the gravitational force acting on the lift and the added weight of the passengers.

As the lift ascends and reaches the top floor, the movement might lead to a constant velocity in certain intervals where the tension stabilizes, indicating that the net forces are equal and there is no further acceleration.

Should the graph indicate sudden changes, this might correlate to the lift stopping or changing speed, where the forces acting on the lift balance out. This analysis indicates that the lift follows a controlled upward motion with periods of acceleration and deceleration based on the variations in the tension force.

Removing one cable from the total of six would affect the distribution of the load on the remaining cables. With only five cables supporting the lift, each remaining cable must now share the weight more heavily.

Given that the load increases on each remaining cable, the extension for these cables can be gauged as:

$ext{New Force} = \frac{12,000 ext{ N}}{5} = 2400 ext{ N per cable}$

Since more force correlates to greater extension (as per the original extension formula), we can expect the extensions to increase as a result. Thus, the remaining cables will undergo greater strain, likely leading to a larger overall extension in the system until the limits of material properties are reached.

In conclusion, the removal of one cable will increase the extension of the remaining cables due to increased tension per cable, which could potentially lead to structural concerns if not addressed.