Final answer:
When an elevator moves upwards with a constant velocity, such as 10 m/s in this scenario, the scale reading reflects the weight of the person, calculated by multiplying their mass with gravitational acceleration (w = mg). For a 70 kg man, the scale reading will be 686.7 N, which is his weight unaffected by the constant velocity of the elevator.
Step-by-step explanation:
The question asks what the scale reading is when a man stands on a weighing scale in an elevator that is moving upwards with a uniform speed of 10 m/s. To determine the scale reading when the elevator is moving at a constant velocity, we can use the concept of Newton's first law of motion which states that an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Since the elevator is moving upwards at a constant velocity (not accelerating), the only two forces acting on the man are his weight (downward) and the normal force from the scale (upward).
Since these forces are balanced (the elevator is not accelerating), the scale reading will be equal to the man's weight, which is the product of mass and gravitational acceleration (w = mg). For a 70 kg man, the weight w is calculated as:
w = (70 kg)(9.81 m/s²) = 686.7 N.
Hence, the scale reading will be 686.7 N. This implies that when an elevator moves upwards with a constant velocity, the person's perceived weight shown on the scale remains the same as if they were standing still on the ground.