Question

A student weighing $500N$ stands on a spring scale in an elevator. If the scale reads $520N$, the elevator must be:

• A. Accelerating upward
• B. Accelerating downward
• C. Moving upward at constant speed
• D. Moving downward at constant speed

Answer 1

The correct option is A Accelerating upward

Given:
Original weight of the student, W = $500N$
Reading on the spring scale is the normal reaction by the scale on the student, and is given as, $N=520N$
The normal reaction acts upwards while the weight of the student acts vertically downward.
Inside the elevator, the magnitude of the normal reaction is greater than the magnitude of the weight.Thus, the net force on the student:
$F=N-W$
$F=520N-500N$
$F=20N$ (Vertically upwards)
Hence, the net force is acting vertically upwards.
Thus, the elevator must be accelerating upwards as the net force acting is upward.