Please answer B,C,D (13%) Problem 8: Suppose the mass of a loaded elevator is 16

Question

Please answer B,C,D

(13%) Problem 8: Suppose the mass of a loaded elevator is 1650 kg 25% Part (a) What force, in newtons' must be supplied by the elevator's cable to produce an acceleration of 0.835 m/s2 upwards against a 225-N frictional force? 25% Part (b) How much work, in joules, is done by the cable in lifting the elevator 19 m? Grade Summary Deductions Potential 0% 100% tan() | | acos) Submissions Attempts remaining: 10 in cosO % per attempt) detailed view atan()acotan( 23 0 cosh) tanh) cotanhO Degrees Radians END BACKSPACE DEL CLEAR Submit Hint I give up! Hints: 1 % deduction per hint. Hints remaining: 1 Feedback: deduction per feedback. 25% Part (c) What is the final speed, in meters per second, of the elevator if it starts from rest? /S 25% Part (d) How much work, in kilojoules, went into thermal energy produced by friction?

Explanation / Answer

a) F = m(g + a) + Ff
F = 1650(9.81 + 0.835) + 225
F = 17789.25
F = 17.8 kN

b.) If we assume the elevator car is initially at rest, work must overcome friction, change the potential energy and accelerate the mass

W = Fd + mgh + ½mv²
d = h

v² = v² + 2as
v² = 0² + 2(0.835)19
v² = 31.73

W = Fd + mgh + ½mv²

W = 225(19) + 1650(9.81)19 + ½(1650)31.73
W = 337995.75
W = 338 kJ

c.) v² = 31.73
v = 5.63 m/s

d) W = 0.5*1650*31.73 = 26177.25 J = 26.2 kJ

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