A particular box has a weight of mg = 50 N (on Earth). If you simply place the b

Question

A particular box has a weight of mg = 50 N (on Earth). If you simply place the box on a table, the table will exert an upward normal force of 50 N on the box. Assume g = 10 N/kg on Earth. (a) If possible, describe two situations in which the table exerts an upward normal force of 60 N on this box. Situation A - the table, with the box on top, is in an elevator. (i) Describe the motion of the elevator, (ii) draw the corresponding free-body diagram of the box, and (iii) apply Newton's second law to show that the normal force is 60 N. Situation B - the table, with the box on top, is one of the tables in our classroom. (i) If possible, describe a situation in which the upward normal force applied by the table on the box is 60 N, (ii) draw the corresponding free-body diagram of the box, and (iii) apply Newton's second law to show that the normal force is 60 N. (b) If possible, describe two situations in which the table exerts an upward normal force of 45 N on this box. Situation C - the table, with the box on top, is in an elevator. (i) Describe the motion of the elevator, (ii) draw the corresponding free-body diagram of the box, and (iii) apply Newton's second law to show that the normal force is 45 N. Situation D - the table, with the box on top, is one of the tables in our classroom. (i) If possible, describe a situation in which the upward normal force applied by the table on the box is 45 N, (ii) draw the corresponding free-body diagram of the box, and (iii) apply Newton's second law to show that the normal force is 45 N.

Explanation / Answer

(A) if table accelerates upward then

Applying Fnet = m a

N - m g = m a

60 - 50 = (50 / 9.8) a

a = 1.96 m/s^2 upward

so this can be attained in two ways:

1. elevator is moving upward and its speed is increasing with rate of 1.96 m/s^2.

2. elevator is moving donward and its speed decreases by this rate.

(B) for N= 45 N

45 - 50 = (50 / 9.8)a

a = -1 m/s^2

1. elevator is moving upward and its speed decreases.

2. elevator is moving downward and its speed increases.

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