A 76 kg man stands on a bathroom scale in an elevator. Starting from rest at the

Question

A 76 kg man stands on a bathroom scale in an elevator. Starting from rest at the bottom floor, the elevator ascends, attaining its maximum speed of 1.35 m/s in 0.79 s. It travels with this constant speed for the next 5.60 s. The elevator then slows down for 1.65 s and comes to rest at the top level.

a) What is the acceleration of the man during the first 0.89 s? Answer in units of m/s2 and use the upward direction as positive.

b) How many forces act on the Man during this elevator ride?

c) What does the bathroom scale register in N during the first 0.89 s?

d) What does the bathroom scale register in N during the 5.60 s period?

e) What does the bathroom scale register in N during the 1.65 s period?

Use 10 N/kg for g and the upward direction as positive.

Explanation / Answer

(a)

a=1.35/0.89-9.8=-8.3m/s2

(b)

gravitational force and upward force due upward acceleration of elevator

(c)

F=mg+ma=76(9.8-8.3)=114N

(d)

During 5.6 Sec period since a is zero

F=mg=76x9.8=-744.8N

(e)

while declerating

a=-1.35/1.65=-0.82m/s2

F=mg+ma=76x10.82=-822.32N

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.