5. A car accelerates from 0 to 72 km/hour in 8.0 seconds. What is the car's acceleration?

An airplane flies at 150 km/hr. (a) The airplane is towing a banner that is b = 0.8 m tall and l = 25 m long. If the drag coef-

maw [93]

Answer:

Power requirement P for the banner is found to be 30.62 W
Power requirement P for the solid flat plate is found to be 653.225 W
Answer for part(c) is explained below in the explanation section and can be summarized as: The main difference between the drags and power requirements of the two objects of same size was due to their significantly different drag-coefficients. The Cd for banner was given, whereas the Cd for a flat plate is generally found to be around 1.28 which is the value we used in our calculations that resulted in a huge increase of power to tow the flat plate
Power requirement P for the smooth spherical balloon was found to be 40.08 W

Explanation:

First of all we will establish variables and equations known that are known to us to solve this question. Since we are given the velocity of the airplane:

v = velocity of airplane i.e. 150 km/hr. To convert it into m/s we will divide it by 3.6 which gives us 41.66 m/s
The density of air at s.t.p (standard temperature pressure) is given as d = 1.225 kg / m^3
The power can be determined this equation: P = F . v, where F represents the drag-force that we will need to determine and v represents the velocity of the airplane
The equation to determine drag-force is: $F = 1/2 * d * C_d * A$

In the drag-force equation Cd represents the co-efficient of drag and A represents the frontal area of the banner/plate/balloon (the object being towed)

Frontal area A of the banner is : 25 x 0.8 = 20 m^2

Part a) We will plug in in the values of Cd, d, A in the drag-force equation i.e. Fd = 1/2 * 0.06* 1.225 * 20 = 0.735 N. Now to find the power P we will use P = F . v i.e. 0.735 * 41.66 = 30.62 W

Part b) For this part the only thing that has fundamentally changed is the drag-coefficient Cd since it's now of a solid flat plate and not a banner. The drag-coefficient of a flat plate is approximately given as : Cd_fp = 1.28

Now we will plug-in our values into the same equations as above to determine drag-force and then power. i.e. Fd = 1/2 * 1.28 * 1.225 * 20 = 15.68 N. Using Fd to determine power, P = 15.68 * 41.66 = 653.225 W

Part c) The main reason for such a huge power difference between two objects of same size was due to their differing drag-coefficients, as drag-coefficients are generally large for objects that are not of a streamlined shape and leave a large wake (a zone of low air pressure behind them). The flat plate being solid had a large Cd where as the banner had a considerably low Cd and therefore a much lower power consumption

Part d) The power of a smooth sphere can be calculated in the same manner as the above two. We just have to look up the Cd of a smooth sphere which is found to be around 0.5 i.e. Cd_s = 0.5. Area of sphere A is given as : pi* r^2 (r = d / 2). Now using the same method as above:

Fd = 1/2 * 0.5 * 3.14 * 1.225 = 0.962 N

P = 0.962 * 41.66 = 40.08 W

4 0

3 years ago

Que distancia se desplaza un objeto que se mueve con velocidad de 72km/h durante 10 min?

Allushta [10]

Answer:

I would love to help, Could you put the question in English?

Explanation:

4 0

2 years ago

Explain how energy balance sets planetary temperature? Imagine a planet colder than expected for energy balance and explain why

RUDIKE [14]

The planetary temperature energy balance is obtained by radiating back the absorbed radiation energy from outer-space, by the planet and thus acquiring thermal equilibrium.

What is the process of attaining thermal equilibrium by Earth?

The Stefan-Boltzmann law states that the more the temperature a planet has, the more it will radiate out to reach thermal equilibrium.

We know that outer space contains large masses of radiative energy freely distributed in its vast expanse. A small fraction of this energy is absorbed by the Earth through the atmosphere, surface land, clouds etc.

Now, radiative balance is achieved when a planet's surface continuously warms up until it reaches its peak at which point the same amount of absorbed energy can then be radiated back to space. The relative amount of energy radiated back by a planet is dependent upon the size of the planet.

A colder planet relatively absorbs lower amount of radiation energy from space. In some time, as the planet heats up enough, the energy is radiated back to the space attaining thermal equilibrium.

Learn more about Stefan-Boltzmann law here:

brainly.com/question/14919749

#SPJ4

6 0

1 year ago

A mass hanged on a spring scale. what is the force exerted by gravity on 700g ?

Ipatiy [6.2K]

Answer:

6.86 N

Explanation:

Applying,

F = mg............... Equation 1

Where F = Force exerted by gravity on the mass, m = mass, g = acceleration due to gravity

Note: The Force exerted by gravity on the mass is thesame as the weight of the body.

From the question,

Given: m = 700 g = (700/1000) = 0.7 kg

Constant: g = 9.8 m/s²

Substitute these values into equation 1

F = 9.8(0.7)

F = 6.86 N

6 0

2 years ago

An airplane has a starting velocity of 300m/s. It then accelerates at a rate of 45m/s2 for a time of 10s. What is it's final vel

Olenka [21]

A = (v - u) / t

a = acceleration
v = final velocity
u = initial velocity
t = time

45 = (v - 300) / 10

45 × 10 = v - 300

450 + 300 = v

v = 750 m/s

Hope this helps!

P.S. Let me know if you need an explanation

8 0

2 years ago