Flooding on rivers is caused by human activity rather than natural events. Please select the best answer from the choices provid
2 answers:
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Answer:
D. Acceleration is always in the same direction as velocity.
Explanation:
First of all, let's remind the definition of acceleration:
Acceleration is equal to the rate of change in velocity, in formula
where is the change in velocity and
is the time interval.
It is important to keep in mind that acceleration is a vector, so it has a direction.
Now let's analyze each statement:
A. Acceleration can be zero, positive, or negative. --> TRUE. When acceleration is positive, it means that its direction is the same as the velocity, so the object is speeding up; when acceleration is negative, it means that its direction is opposite to the velocity, so the object is slowing down; when acceleration is zero, the object has constant velocity.
B. An object can have acceleration with zero velocity. --> TRUE. In fact, an object can be moving with a positive velocity and having a constant negative acceleration: this means that its velocity will decreases until it becomes zero and then it turns negative. At the moment the velocity is zero, the acceleration is not zero.
C. An object can have acceleration with negative velocity. --> TRUE. The direction of the acceleration does not depend on the direction of the velocity: an object with negative velocity is moving in the direction opposite to that used as reference, so it can still have an acceleration.
D. Acceleration is always in the same direction as velocity. --> FALSE. As we we said in point a and c, the direction of the acceleration does not depend on the direction of the velocity, so an object with positive velocity, for example, can have a negative acceleration (it means that the acceleration is in the opposite direction, so the object is slowing down).
Hi!
The correct answer would be: the width of I-bands
The sacromere is the smallest contractile unit of striated muscles. These units comprise of filaments (fibrous proteins) that, upon muscle contraction or relaxation, slide past each other. The sacromere consists of thick filaments (myosin) and thin filaments (actin).
<em>Refer to the attached picture to clearly see the structure of a sacromere.</em>
<u>When a sacromere contracts, a series of changes take place which include:</u>
<em>- Shortening of I band, and consequently the H zone</em>
<em>- The A line remains unchanged</em>
<em>- Z lines come closer to each other (and this is due to the shortening of the I bands) </em>
The only changes that take place occur in the zones/areas in the sacromere (as mentioned), not in the filaments (actin and myosin) that make the up the sacromere; hence all other options are wrong.
Hope this helps!
