Argelia has a stack of schoolbooks sitting in the backseat of her car. When Argelia makes a sharp right turn, the books slide to
2 answers:
Answer:
The books slide to the left due to inertia, and then they come to a rest due to the force applied by the car door.
Explanation:
The entire motion of the books can be explained by using the first two laws of Newton:
- 1st Newton's law (also called Law of Inertia): an object at rest stays at rest and an object in motion stays in motion with constant velocity if no unbalanced forces act on it
- 2nd Newton's law: when an object is acted upon unbalanced forces, an acceleration is induced in the motion of the object, according to the equation
where F is the net force on the object, m is its mass and a is its acceleration.
Coming back to our problem:
- At the beginning, Argelia makes a sharp turn right. Due to the law of inertia, the books (which are not fixed to the car) continue their motion straight as it was before the curve: so, since the car is moving right, they appear to go the left of the car.
- When the books hit the car door, they stop moving due to the 2nd Newton's law: in fact, the car door applies an unbalanced force against the books, and as a result the books have a negative acceleration (=deceleration), so they slow down and eventually they stop.
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Answer:
When blueshift happens, the perceived frequency of the wave would be higher than the actual frequency.
Explanation:
As the name suggests, when blueshift happens to electromagnetic waves, the frequency of the observed wave would shift towards the blue (high-frequency) end of the visible spectrum. Hence, there would be an increase to the apparent frequency of the wave.
Blueshifts happens when the source of the wave and the observer are moving closer towards one another.
Assume that the wave is of frequency at the source. In other words, the source of the wave sends out a peak after every
.
Assume that the distance between the observer and the source of the wave is fixed. It would then take a fixed amount of time for each peak from the source to reach the observer.
The source of this wave sends out a peak after each period of . It would appear to the observer that consecutive peaks arrive every
. That would correspond to a frequency of
.
On the other hand, for a blueshift to be observed, the source of the wave needs to move towards the observer. Assume that the two are moving towards one another at a constant speed of .
Again, the source of this wave would send out a peak after each period of . However, by the time the source sends out the second peak, the source would have been
closer to the observer then when the source sent out the first peak.
When compared to the first peak, the second peak would need to travel a slightly shorter distance before it reach the observer. Hence, from the perspective of the observer, the time difference between the first and the second peak would be shorter than . The observed frequency of this wave would be larger than the original
.