Physics, 16.03.2020 20:07 sjeueujs2067

Somewhere in the vast flat tundra of planet Tehar, a projectile is launched from the ground at an angle of 40 degrees. It reaches the maximum height of 30 m. The acceleration due to gravity is 30 m/s2. Part 1. Find the time t the projectile spends in the air.

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Answer from: jlchandl

2.83 s

Explanation:

Let v be the initial launching velocity of the projectile. This can be split into 2 components:

- Horizontal component $v_h = vcos\theta = vcos40^o = 0.766 v$

- Vertical component $v_v = vsin\theta = vsin40^o = 0.643 v$

For the vertical motion, only affected by vertical velocity and gravitational acceleration g = 30 m/s2. As the object reaches maximum height, we can use the following equation of motion to find out the initial velocity of the projectile:

$v^2 - v_0^2 = 2a\Delta s$

where v = 0 m/s is the final velocity of the object when it stops at the max height, v_0 = v_v = 0.643 v is the initial vertical velocity of the object when it start, a = -30 m/s2 is the deceleration of the can, and $\Delta s = 30$ is the maximum distance traveled.

0 - (0.643v)^2 = 2*(-30)*30

(0.643v)^2 = 1800

$0.643v = \sqrt{1800} = 42.43 = v_v = v_0$

v = 42.43 / 0.643 = 66 m/s

Then we can also apply the following equation of motion to solve for the time it takes to reach maximum height of 30m

$\Delta s = v_0t + at^2/2$

30 = 42.43 t - 30t^2/2

15t^2 - 42.43t + 30 = 0

t^2 - 2.83t + 2 =0

As $2.83 = 2*1.415 \approx 2*\sqrt{2}$ we have a case of (a - b)^2 = a^2 - 2ab + b^2 . The equation of t can be rewritten as

$(t - \sqrt{2})^2 = 0$

$t - \sqrt{2} = 0$

$t = \sqrt{2} \approx 1.415 s$

Since it would take another t seconds to fall down and hit the ground. The total time the projectile would spend on air is 2*1.415 = 2.83 s

Answer from: Quest

nec chapter 5 contains

c. information on special occupancy areas

nec chapter 6 covers

a. special equipment

which of the following rules contain the words shall or shall not and must be adhered to?

b. mandatory rules

which of the following rules identify actions that are allowed but not required and typically cover options or alternative methods?

c. optional rules

which of the following serves as the introduction to the nec and provides an overview of the book?

a. nec article 90

organizations that test products for safety are

c. nrtls

the nec is published by the

a national fire protection association

the nec is divided into

b. 9 chapters

the nec provides informative annexes for

c. informational materials and examples

two terms from nec article 100 that trainees should become familiar with are

b. labeled and listed

explanation:

Answer from: Quest

The answer is a 0.64 volts

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