Let’s ride on an Elevator

What happens to your weight as you ride on an elevator?

N - is the normal force

What is your weight if the elevator is not moving?

We know that the acceleration is zero.

So the net force is zero So the upward force of the floor (N) is equal to your weight.

A note about Scales ….

When the elevator starts accelerating upward?

N The acceleration is upward so the net force is upward also + a F net = ma N – W = ma N = W + ma W So you feel heavier

The elevator starts accelerating downward?

N The acceleration is downward so the net force is downward F net = ma a W – N = ma N = W - ma + W So you feel lighter

OH NO… the cable breaks… The acceleration is downward so the net force is downward a + F net = mg W – N = mg N = W - mg N = 0 W So you feel weightless

The Vomit Comet was the nickname given to the aircraft used by NASA 's Reduced Gravity Research Program . The plane makes reduced gravity parabolic flight paths, allowing the occupants to experience during the parabola. By modifying the flight path, any value for the apparent gravity may be produced.

http://www.youtube.com/wat ch?v=2V9h42yspbo

In general it is used to train astronauts in zero-g maneuvers, giving them about 25 seconds of weightlessness flight.

out of 65 seconds of The source of the nickname, of course, should be apparent.

http://www.youtube.com/wat ch?v=wSTLBc-4q60

In 2005 , NASA replaced the aircraft with a McDonnell Douglas C-9. One was used for filming scenes involving weightlessness in the movie

Apollo 13

; that aircraft was retired in 2000 and is now on display at Ellington Field , near the Johnson Space Center . The other made its final flight on 29 Oct 2004, and is to be permanently stored in the AMARC storage facility in Arizona.

http://www.youtube.c

om/watch?v=8JC6dci0 6Gc

1. Otis L. Evaderz is conducting his famous elevator experiments. Otis stands on a bathroom scale and reads the scale while ascending and descending the John Hancock building. Otis weighs 1000 N, but notices that the scale readings depend on what the elevator is doing. Use a free-body diagram and Newton's second law of motion to solve the following problems.

a. What is the scale reading when Otis accelerates upwards at 0.50 m/s 2 ? N F net = ma N – W = ma + a N = W + ma N = 1000 N +100 kg(.5m/s 2 ) W N = 1050 N

b . What is the scale reading when Otis is traveling upward at a constant velocity of at 2 m/s? Depress mouse to view answer.

c. As Otis approaches the top of the building, the elevator slows down at a rate of 0.50 m/s 2 . Be cautious of the direction of the acceleration. What does the scale read?

Depress mouse to view answer.

d. Otis stops at the top floor and then accelerates downwards at a rate of 0.50 m/s 2 . What does the scale read? Depress mouse to view answer.

e. As Otis approaches the ground floor, the elevator slows down (an upwards acceleration) at a rate of 0.50 m/s 2 . Be cautious of the direction of the acceleration. What does the scale read? Depress mouse to view answer.

What is the tension in the cable if the box has a weight of 1600N and the man 300N?

F net = (m man + m box ) a T - W man - W box = (m man + m box ) a T = W man + W box + (m man + m box ) a T= 300 N + 1600 N + (30 kg +160 kg) 0.620 m/s 2 T = 2017.8 N