Question
Unreasonable Results: A 75.0-kg man stands on a bathroom scale in an elevator that accelerates from rest to 30.0 m/s in 2.00 s. (a) Calculate the scale reading in newtons and compare it with his weight. (The scale exerts an upward force on him equal to its reading.) (b) What is unreasonable about the result? (c) Which premise is unreasonable, or which premises are inconsistent?

a) $2.53$

b) The elevator acceleration is more than 2 times his weight. He will probably fall down. Elevators are not built to be so uncomfortable.

c) The final speed is too high. An elevator doesn't need to get 110 km/h.

Solution Video