4. A 65 kg woman is inside an elevator. Calculate her apparent weight (Normal Force) for the following cases: a. The elevator moves at constant speed of 10 m/s downward (2 pts)
b. The elevator accelerates upward at a constant rate of 2.4 m/s2 (2 pts)
c. If the scale read 450 N. Find the magnitude and direction of the elevator’s acceleration. (3 pts)

Explanation:

a ) Let her apparent weight be W₁

Net force on her = W₁ - mg

acceleration a = 0

W₁ - mg  = 0

W₁   =   mg = 65 x 9.8 = 637 N  

b )

a = 2.4 m /s²

W₁ - mg  = ma

W₁  = m(g + a )

= 65 x ( 9.8 + 2.4 )

= 793 N

c )

W₁ = 450 N

a = ?

W₁ - mg  = ma

450 - 65 x 9.8 = 65 x a

65 a = - 187

a = - 2.87 m /s²

acceleration is negative therefore , it must be downwards   .

e) none of the above answers are correct

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