A 50.0 kg man standing on a spring scale takes a descending elevator ride (DOWNWARD). Starting from the rest, the elevator descends, attaining a maximum speed of 8.0 m/s in 4.0 seconds. Then the elevator travels with this constant speed of 8.0 m/s for 10.0 seconds. Lastly, it takes the elevator 2.0 second to make a complete stop. Based on the information above, answer the questions below:
A 50.0 kg man standing on a spring scale takes a descending elevator ride (DOWNWARD). Starting from the rest, the elevator descends, attaining a maximum speed of 8.0 m/s in 4.0 seconds. Then the elevator travels with this constant speed of 8.0 m/s for 10.0 seconds. Lastly, it takes the elevator 2.0 second to make a complete stop. Based on the information above, answer the questions below:
(Hint: Drawing pictures would help you understand the 3 legs of this elevator ride. Since the elevator is descending, going down, it is more convenient to chose downward direction as + direction. Please pay attention to the sign of each physical quantity, such as velocity, acceleration, and displacement, etc.
Useful formula: v = vi + a×t, or
d = v0×t + ½ a × t2,
Weight = mg,
Newotn’s 2nd Law: Net force Fnet = ma
(1). What is the acceleration of the elevator during the 1st 4.0 seconds of the ride? Is the direction of the acceleration upward or downward?
(2). How far does the elevator travel during this time?
(3). What is the true weight (W) of the man?
(4). What is the net force (F) acting on the man required to produce the acceleration?
(5). What is the force (N) exerted on the man’s feet by the floor of the elevator.
(6). What is the apparent weight of the man in Newtons?
(7). What is the acceleration of the elevator during the following 10.0 seconds of the ride?
(8). How far does the elevator travel during this 10.0-second period?
(9). What is the net force (F) acting on the man required to produce the acceleration?
(10) What is the force (N) exerted on the man’s feet by the floor of the elevator.
(11). What is the apparent weight of the man in Newtons?
(12). What is the acceleration of the elevator during the last 2.0-second of the ride? Is it upward or downward?
(13). How far does the elevator travel during this 2.0-second period?
(14). What is the net force (F) acting on the man required to produce the acceleration?
(15). What is the force (N) exerted on the man’s feet by the floor of the elevator.
(16). What is the apparent weight of the man in Newtons?
(17). What is the total distance the elevator travels during this whole ride.
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