Answer:
1: 19,6 N | 2: 686 N | 3: 705,6 N
Explanation:
Just apply the formula:
1: 2 . 9,8 = 19.6 N
2: (60+10) . 9,8 = 686 N
3: [30 + (6 . 7)] . 9,8
[30 + 42] . 9,8
72 . 9,8 = 705.6 N
Just sum all the weights in the system and then multiply by gravity (9,8 in this case)
1. A. 6.00 sec
The graph shows the velocity of an object (y-axis) versus the time (x-axis). In order to find when the magnitude of the velocity reaches 36.00 km/h, we should find the time t (x-coordinate) at which the velocity (y-coordinate) is 36.
By looking at the graph, we see that this occurs when t=6.00 s.
2. A. positive acceleration
In a velocity-time graph like this one, the slope of the curve corresponds to the acceleration of the object. In fact, acceleration is defined as:
where 
is the variation of velocity and 
is the variation of time. We see that this quantity corresponds to the slope of the curve in the graph (in fact, represents the increment of the y coordinate, while represents the increment of the x coordinate). So, a positive slope means a positive acceleration: in this case, the slope is positive, so the acceleration is also positive.
The ancient Greeks, in a theory that was suggested around 450 BC, believed that everything was from from four elements. These elements included earth, water, air and fire. Later, Aristotle supported this theory.
Therefore, the first option is correct.
They are slowed down.
even air is a medium and will slow down waves (slightly) compared to a vacuum/ space
if the wave hits the medium at an angle it can be 'bent' (refracted) like light through a glass prism
Answer:
Oxygen and methane can react chemically with each other, so we would not see them together unless there are active sources for both. On Earth, biology is responsible for essentially all the oxygen and the majority of the methane in our atmosphere.
