Which type of simple machine is in the photo?

A hot air balloon is traveling vertically upward at a constant speed of 4.5 m/s. When it is 28 m above the ground, a package is

ella [17]

Answer:

1.97 seconds

Explanation:

t = Time taken

u = Initial velocity

v = Final velocity

s = Displacement

a = Acceleration due to gravity = 9.8 m/s²

$s=ut+\frac{1}{2}at^2\\\Rightarrow 21=4.5t+\frac{1}{2}\times -9.8\times t^2\\\Rightarrow 21=-4.5t-4.9t^2\\\Rightarrow 4.9t^2+4.5t-28=0\\\Rightarrow 49t^2+45t-280=0$

Solving the above equation we get

$t=\frac{-45+\sqrt{45^2-4\cdot \:49\left(-280\right)}}{2\cdot \:49}, \frac{-45-\sqrt{45^2-4\cdot \:49\left(-280\right)}}{2\cdot \:49}\\\Rightarrow t=1.97, -2.89$

So, the time the package was in the air is 1.97 seconds

3 0

3 years ago

Which one of the following temperatures (in °C) is equivalent to 294 K?

vaieri [72.5K]

Answer:

21

Explanation: its actually 20.85 but i guess they round to 21

5 0

3 years ago

Which of the following statements is part of the theory?

IceJOKER [234]

The answer isn't here. All sites say the answer is Only animals are composed of cells. More than one site says this.
Holes I helped

4 0

3 years ago

Read 2 more answers

Question 27 a motorboat takes 3 hours to travel 144km going upstream. the return trip takes 2 hours going downstream. what is th

Vedmedyk [2.9K]

In this item, we let x be the rate of the boat in still water and y be the rate of the current.

Upstream. When the boat is going upstream, the speed in still water is deducted by the speed of the current because the boat goes against the water. The distance covered is calculated by multiplying the number of hours and the speed.
(x - y)(3) = 144

Downstream. The speed of the boat going downstream is equal to x + y because the boat goes with the current.
(x + y)(2) = 144

The system of linear equations we can use to solve for x is,
3x - 3y = 144
2x + 2y = 144

We use either elimination or substitution.

We solve for the y of the first equation in terms of x,
y = -(144 - 3x)/3

Substitute this to the second equation,
2x + 2(-1)(144 - 3x)/3 = 144
The value of x from the equation is 60

<em>ANSWER: 60 km/h</em>

5 0

3 years ago

A certain thin lens is made of glass with refraction index ????lens=1.500. In air, where the index of refraction is 1.000, the l

son4ous [18]

Answer:

The focal length of the lens in ethyl alcohol is 41.07 cm.

Explanation:

Given that,

Refractive index of glass= 1.500

Refractive index of air= 1.000

Refractive index of ethyl alcohol = 1.360

Focal length = 11.5 cm