Physics, 10.11.2019 03:31 Tyrant4life

Aplayer kicks a soccer ball in a high arc toward the opponent's goal. at the highest point in its trajectory a) both the velocity and the acceleration of the soccer ball are zero. b) neither the ball's velocity nor its acceleration are zero. c) the ball's velocity points downward. d) the ball's acceleration points upward. e) the ball's acceleration is zero but its velocity is not zero.

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Answer from: alyssabailey7545

b) True. The horizontal speed is different from zero and the vertical acceleration is different from zero

Explanation:

Let's analyze the problem using the two-dimensional kinematic equations specifically for projectile launches.

As the ball is on the ground, it pulls it at all times with an acceleration directed to the center of the earth, specifically the acceleration of gravity.

At the highest point of the trajectory the ball does not rise any more, so the vertical speed is zero. In general, on the x-axis (horizontal) the friction force can exist, which in many cases can be neglected, but there is a horizontal velocity.

Now let's analyze if the statements are correct.

a) False. We saw that the horizontal speed is different from zero

b) True. The horizontal speed is different from zero and the vertical acceleration is different from zero

c) False. The vertical speed is zero, so the speed is horizontal that points in the direction of the x-axis

d) False. The acceleration is vertical

e) False. The acceleration is not zero

Answer from: Quest

It's have to be 12 or idk

Answer from: Quest

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

$x(t)=ax(x-6)$

where $a$ is unknown. because the position is parabolic, there is symmetry about the midpoint at $t=3$ , and we know that

$x(3)=10\implies -9a=10\implies a=-\dfrac{10}9$

so that the position function is

$x(t)=-\dfrac{10}9x(x-6)$

which means the velocity is

$v(t)=\dfrac{\mathrm dx}{\mathrm dt}=-\dfrac{20}9x+\dfrac{60}9$

then the total distance traveled is

$\displaystyle\int_{t=0}^{t=6}|v(t)|\,\mathrm dt=\left\{\int_{t-0}^{t=3}-\int_{t=3}^{t=6}\right\}v(t)\,\mathrm dt=20$

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at $x=0$ and ends at $x=0$ , so its displacement is 0.

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Aplayer kicks a soccer ball in a high arc toward the opponent's goal. at the highest point in its tr...