To determine the correct conclusion about the motion of the lift based on the given information, let's analyze the forces and the scenario step-by-step.
1. Understanding the Forces:
- The girl's weight is 600 N. This is the gravitational force acting downwards.
- The scale reading is 560 N. This is the normal force exerted by the scale, which is the force the girl exerts on the scale and is equal to the reading observed.
2. Comparing the Forces:
- When the lift is not accelerating (moving at constant velocity either upwards or downwards, or at rest), the reading on the scale matches the girl's actual weight, which in this case would be 600 N.
- In this scenario, the scale reads 560 N, which is less than her actual weight.
3. Reasoning About the Motion:
- Since the scale reads less than the actual weight, it indicates that the normal force is less than the gravitational force.
- A reduced normal force implies that there is an additional downward force component acting on the girl. This would mean that the lift must be accelerating downwards, causing the girl to have an apparent weight that is less than her actual weight.
Thus, the correct conclusion about the motion of the lift is:
B. accelerating downwards.
