Imagine a ball is moving on the following horizontal line.
. . . . . . . . . . . . . . . . . . . O. . . . . . . . . . . . . . . . . .
Take right as positive. O is the starting point of the ball. Denote the ball by o.
. . . . . . . . . . . . . . . . . . . O. . . . . . . ... . . o . . . . . .
Assume the ball is moving to the right. It has positive displacement since it is on the right of O, and positive velocity since its positive displacement is increasing.
.ñ
. . . . . . . . . . . . . . . . . . . O. . . . o . . . . . . . . . . . . .
Now the ball is returning to O. It still has positive displacement since its current position is still on the right of O. However, its velocity is negative since its positive displacement is decreasing and the direction of the velocity vector points left, which is the negative side.
By now you should be able to come up with a scenario where the ball has negative displacement and positive velocity.
You can observe the same phenomenon in daily life. Say, as a stretched spring bounces to its starting position, if we let the returning direction be positive, the string has negative displacement since it is on the negative direction, but has positive velocity. Bungee jump can also used to illustrate the phenomenon.
Answer:
D. 3 hours or more
Explanation:
The average 8- to 18-year-old spends at least D. 3 hours every day in front of a screen, performing little to no physical activity. This is because, instead of exercising and socializing with their peers, children and teenagers frequently talk, watch a lot of movies/shows, or play video games on their computers. Unfortunately, this is typically considerably more than three hours every day. Although some children still prefer physical activities over this, the bulk of the population does not.
-- loud sounds
-- bright lights
-- strong radio signals
-- Slinkies that can pinch you painfully
-- a tsunami in the ocean
-- earthquakes above Richter 5 or 6
