Answer to Question #143145 in Physics for Kiara Mcdowell

Question

3. A 5 kg lemon (i.e. a very large lemon) is placed on the floor of an elevator near the top floor of a tall building. The elevator descends toward the ground floor. As the elevator approaches the ground floor it begins to slow down. While the elevator is slowing down, the normal force on the lemon will
(a) be greater than 49 N.
(b) be 49 N.
(c) be less than 49 N.
(d) fluctuate between greater than 49 N and less than 49 N as the elevator slows down.

Answer 1

While the elevator is slowing down, the force which causes deceleration is directed upward. Thus, the forces acting of the lemon obey the second Newton's law (in projection on the y-axis directed upward):

$$ma = -mg+N$$

where $N$ is the normal force. Thus, obtain:

$$N = mg +ma$$

Since $mg = 49N$, the normal force will be greater than 49 N.

Answer. (a) be greater than 49 N.