You stand on a spring scale on the floor of an elevator . Of the following, the scale shows the minimum reading when the elevator： (The magnitude of acceleration is same.)
A: moves upward with increasing speed
B: moves upward with decreasing speed
C: remains stationary
D: moves downward with decreasing speed
A: moves upward with increasing speed
B: moves upward with decreasing speed
C: remains stationary
D: moves downward with decreasing speed
举一反三
- Given: function[img=34x25]17de81e321f7032.png[/img] has a second-order derivative within the interval of [img=8x19]17de81e32caa1a1.png[/img], and . Then, within the interval of , the curve is: A: increasing and convex upward B: decreasing and convex upward C: increasing and convex downward D: decreasing and convex downward
- As a block slides down a frictionless incline, which of the following statements is true? A: Both its speed and acceleration increase. B: Its speed and acceleration remain constant. C: Its speed increases and its acceleration remains constant. D: Both its speed and acceleration decrease. E: Its speed increases and its acceleration decreases. F: None of these.
- The supply curve slopes upward when graphed against ________, because of ________. A: the price of the good; increasing marginal cost B: the price of the good; decreasing marginal cost C: income; increasing marginal cost D: income; decreasing marginal cost
- When a body moves in a straight line at the speed [img=80x20]1803e2495cd4c09.png[/img], then the distance traveled by the object in the time interval [img=35x25]1803e2496523c5f.png[/img] is [img=178x51]1803e2497105aa4.png[/img].
- When determining the coordinate system of the CNC machine tool, which of the following principles is adopted for the movement relationship between the tool and the workpiece? ( ) A: Assuming the tool moves, the workpiece is stationary B: Assuming the workpiece moves, the tool is stationary C: It depends on the situation D: Assuming that the tool and workpiece are not moving