Consider an elevator in a tall building. The elevator is initially at rest on a floor that is neither the highest nor lowest floor, At time t = 0, the doors of the elevator begin to close. The acceleration of the elevator from time
= 0 to time - 25 seconds is shown in the graph above. Let the positive direction be upward.
(a)
Is the elevator moving upward, moving downward, or at rest at time t = 12 seconds? If the elevator is
moving, state its speed. In any case, explain your reasoning.
(b)
Is the elevator moving upward, moving downward, or at rest at time t = 22 seconds? If the elevator is
moving, state its speed. In any case, explain your reasoning.

20. threshold braking in the vehicle's braking system occurs when a. the brake pedal is pushed, heel on floorboard, with full foot pressure. b. the brakes are exerting full braking power, without traction loss. c. the driver begins pushing down the brake pedal, with moderate slowdown. d. the brakes just begin to take hold with a gradual slowdown.

Awater balloon launcher uses an elastic band with a spring constant of 115 n/m to use thee launcher you stretch thee band back with a balloon n it the water balloons have a mass of 1.3 kg a) if you stretch the band by 0.8 m, what elastic force will the band exert? b) with the band stretched 0.8 m, how much elastic potential energy is stored in the spring? c) if you release the band, it pushes forward. what is the kinetic energy of the balloon when it reaches the natural length of the band? d) what is the speed of the balloon when it reaches the natural length of the band?

1. when conducting a test on what kind of music increases the growth of plants, all of the following would fail to meet to fair test standard except (1 point) using different kinds of plants. giving some plants more water than others. exposing the plants to different types of music. using nutrient-rich soil for one and lesser soil for others. 2. engineering uses scientific thinking to solve real-world problems. (1 point) true false 3. what does it mean to test a hypothesis? (1 point) pass a quiz on other scientists’ results analyze only the results from scientific sources not make assumptions about how an experiment will turn out see if the results of an experiment are what the scientist predicted