Elevator could be moving downward and speeding up / moving upward and speeding up . A student of mass 50 kg stands on a scale in an elevator. The scale reads 800N.
Based on the given scale reading of 800N, the elevator could be moving downward and speeding up (option B) or moving upward and speeding up (option C).
The scale reading of 800N indicates the normal force exerted by the scale on the student. The normal force is equal in magnitude and opposite in direction to the net force experienced by the student.
Let's analyze the options given:
(A) Moving downward and slowing down:
If the elevator is moving downward and slowing down, the net force on the student would be directed upward. In this case, the scale reading would be less than the student's weight, which is 50 kg * 9.8 m/s^2 = 490N. Therefore, option (A) is not possible.
(B) Moving downward and speeding up:
If the elevator is moving downward and speeding up, the net force on the student would also be directed downward. In this case, the scale reading would be greater than the student's weight, as the net force would include both the weight and an additional force due to acceleration. Therefore, option (B) is possible.
(C) Moving upward and speeding up:
If the elevator is moving upward and speeding up, the net force on the student would be directed upward. In this case, the scale reading would be greater than the student's weight, as the net force would include both the weight and an additional force due to acceleration. Therefore, option (C) is possible.
(D) Moving upward and slowing down:
If the elevator is moving upward and slowing down, the net force on the student would also be directed downward. In this case, the scale reading would be less than the student's weight, which is 50 kg * 9.8 m/s^2 = 490N. Therefore, option (D) is not possible.
Based on the given scale reading of 800N, the elevator could be moving downward and speeding up (option B) or moving upward and speeding up (option C).