A watermelon is thrown down from a skyscraper with a speed of 7.0\,\dfrac{\text m}{\text s}7.0 s m 7, point, 0, space, start f
2 answers:
Answer:
y = 17,89 m
Explanation:
Let us fixate the reference point in top of the building, from where the watermelon is thrown down. We will assume also that the positive axis of our system points up. We describe the watermelon’s motion with the equation:
Clearing the equation so we isolate y we have that:
Making a substitution with the values from the statement we have:
]
So, this skyscraper is about 17,89 m tall; which is not very tall for a skyscraper but who am I to judge. 17,89 m is also the displacement of the watermelon from the point it was thrown down.
I hope everything was clear with my explanation. If I can help with anything else, just let me know. Have an awesome day :D
Answer:
j
Explanation:
First, let's write all the data for this exercise.
The initial speed is
The final speed is
If we ignore air resistance, we can use the following equation to calculate the distance travelled by the watermelon in this freefall motion :
(I)
Where is the final speed
Where is the initial speed
Where is the acceleration due to gravity
And where is the distance traveled by the object
The gravity acceleration has a positive sign if we consider as positive the sense of the free fall motion (downward positive sense).
If we replace all the data in the equation (I) :
The value of g is ⇒
Now, if we want to give a value to the displacement vector, we continue with our reference system (which we considered positive downward sense)
j
Where j is the unitary vector that gives to the displacement the vectorial character.
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Answer:
Work done by the spring is negative
Explanation:
We can answer this question by thinking what is the force acting on the box.
In fact, the force acting on the box is the restoring force of the spring, which is given by Hooke's Law:
where
k is the spring constant
x is the displacement of the box with respect to the equilibrium position of the spring
The negative sign in the equation indicates that the direction of the force is always opposite to the direction of the displacement: so, whether the spring is compressed or stretched, the force applied by the spring on the box is towards the equilibrium position.
The work done by the restoring force is also given by
where
F is the restoring force
x is the displacement
is the angle between the direction of the force and the displacement
Here we know that the force is always opposite to the displacement, so
Which means that the work done by the spring is always negative, since the direction of the restoring force is always opposite to the direction of motion.