A student submits their data from the elevator lab to...

A student submits their data from the elevator lab to you without any descriptions. All you have is this plot of the force from the spring scale in the elevator as they rode, measuring the normal force applied to the student. Each straight line segment on the plot is labeled. Answer the following questions about their motion, assuming they pressed only a single button after entering the elevator. Force (N) 0 800 700 0 5 10 15 Time (s) A. Did they go to a higher floor or a lower floor? B. What is the student's mass? C. For what lettered segments is the speed of the elevator constant? D. Find the maximum magnitude of the elevator's acceleration while it's stopping.

Transcript

00:02 Hi, here in this question number one, reading of the scale, bathroom scale in the stationary elevator that will be actually equal to the real weight of the person.

00:53 Means we can say that is equal to m into g, w is equal to m into g where m is the mass of the person and that is given as 712.

01:03 Newton.

01:05 Now there are three phases.

01:11 In the phase one, elevator is being accelerated upward with the acceleration a1 is equal to 2 .0 meter per second square.

01:40 In the phase 2, accelerator means elevator that is moving up with constant speed so in that case acceleration will be zero and in the third phase it is slowing down in the same upward direction with acceleration a 3 and this will be negative this time minus 2 .0 meter per second square in the first part of the problem, we have to draw a diagram to represent the motion of the person in the elevator.

02:43 So suppose this is the elevator, this is the person standing there in the elevator over the bathroom scale.

02:54 Mass of the person that will be acting vertically downward.

02:58 So, normal reaction exerted by the bathroom scale over the person n, that will be acting upward.

03:08 And acceleration in the motion of the elevator that is always, that is also in upward direction.

03:16 So motion diagram of the elevator that is as shown here.

03:35 Now in the second part of the problem, we have to draw the free body diagram means we have to obtain the equations in three different phases.

03:50 In the first phase, when the elevator is accelerated upward, so n should be more than his weight, m g, and that net 4 should be equal to m into a...

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