Physics, 04.12.2020 14:20 deepspy599otchpd

a ball is thrown with a speed of 17.7 m/s at an angle of 49.8° above the horizontal. how much time does the ball need to reach a height of 4.7 m above the release point ?

Answers: 2

Show answers

Answers

Answer from: kaileyy06

The ball needs approximately $0.41\; \rm s$ to reach that height for the first time.

Explanation:

The initial speed of the ball $17.7\; \rm m \cdot s^{-1}$ . However, what would be the initial vertical speed of this ball?

The angle of elevation is $\theta = 49.8^\circ$ . Consider the initial speed of this ball as the length of the hypotenuse of a right triangle. If the angle of elevation is one of the two acute angles of this triangle, the initial vertical speed of this ball would be the leg opposite to that angle.

$\displaystyle \sin \theta = \frac{\text{opposite}}{\text{hypotenuse}}$ .

$\displaystyle \sin \theta = \frac{v(\text{vertical, initial})}{v(\text{initial})}$ .

Therefore:

$\begin{aligned}&v(\text{vertical, initial})\\ &= v(\text{initial}) \cdot \sin\theta \\ &= 17.7\; \rm m \cdot s^{-1} \times \sin \left(49.8^\circ\right) \approx 13.5\; \rm m \cdot s^{-1}\end{aligned}$ .

Let denote the time (in seconds) required for the ball to reach a height of $4.7\; \rm m$ .

Let denote the acceleration because of gravity (typically $g \approx 9.81\; \rm m \cdot s^{-2}$ near the surface of the earth.) The height of the ball seconds after it was thrown would be: $\displaystyle \frac{1}{2}\, g \cdot t^{2} + v(\text{vertical, initial}) \cdot t$ .

Assume that $g \approx 9.81\; \rm m \cdot s^{-2}$ . Set the value of this expression for height to $4.7\; \rm m$ and solve for :

$\displaystyle \frac{1}{2} \times 9.81 \, t^{2} + 13.5 \, t = 4.7$ .

Either $t \approx 0.41$ or $t \approx 2.3$ will satisfy this equation. Both of these two values are reasonable. The first value for ( $0.41\; \rm s$ ) is the time required for the ball to reach a height of $4.7\; \rm m$ for the first time. The second value ( $2.3\; \rm s$ ) is the time required for the ball to come under that height on its way back to the ground. The question seems to be asking only for the first (the smaller one) of these two times.

Answer from: Quest

i dont think you are wrong for wanting to get even with someone who did you wrong.

(i'm an eye for an eye kind of person) but if this person hurt you in a sexual way, i dont suggest doing anything to him. he should be taken to the proper authorities, you could go to jail depending on what you do. if it was something small like your sibling took your spot on the couch, than yea, i would get even with him by taking one of his favorite snacks lol. but i dont suggest you doing anything illegal.

Answer from: Quest

answer would be letter choice (a), a ball resting on a shelf. would be another example of potential energy > stored energy > not moving.

a ball spinning on a finger > kinetic energy > moving energy

a ball rolling on the ground > kinetic energy > moving energy

a ball flying through the air > kinetic energy > moving energy

hope that : )