SHOW WORK WITH UNITS, HIGHLIGHT FINaL ANSWER A 75-kg student is entering an elev
ID: 1334775 • Letter: S
Question
SHOW WORK WITH UNITS, HIGHLIGHT FINaL ANSWER
A 75-kg student is entering an elevator on the 8th floor of the library and steps on a bathroom scale that happens to be there. The student pushes the button to the 2nd floor: the doors close and the elevator speeds up and then continues to move at a constant speed. As things go in the busy library other students on the 4th floor had pushed the call button and the elevator starts to slow down at a constant rate of 0.68 m/s^2 and eventually stops at the 4th floor. While the elevator slows down, what is the reading of the scale? Convert your answer to pounds and use lbs as units. (Practice how to properly work this out. Start with a sketch of the situation. Then draw a proper force diagram, aka free-body diagram. Explain your diagram. Apply Newton's Law and find the answer. Practice how to explain all your steps along the way: what you are doing and why; explain why you are drawing the diagram the way you do. Finally, evaluate your answer.)Explanation / Answer
here ,
mass of the student , m = 75 kg
deaccelration of the elevator , a = 0.68 m/s^2
as the accelration of the lift is upwards
therefore by third law of motion
a force m*a also acts on the student in the opposite direction of motion of the student
let N be the normal reaction force
N = m*g + m*a
N = 75*9.8 + 75*0.68
N = 786 N
N = 176.7 lbs
the reading of the scale is 176.7 lbs
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