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3 years ago

If a car travels 80 miles between 2 and 4 pm, then its velocity is close to 40 mph at 2 pm.

1 answer:

3 0

The answer should be false because it doesnt say if the car is traveling at constant speed. The cars speed can be various so that in total for 2 hours that it travels it passes 80 miles. If however it actually traveled at constant speed than the answer is true.

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HELP URGENT!!!!!!!!!!!!!!!!!!!!!!!!

nirvana33 [79]

D
Because the rest of the answers are illogical

5 0

3 years ago

A balloon of diameter 20.0 cm is filled with helium gas at 30°C at 1.00 atm. How

bogdanovich [222]

Answer:

N = 3.54 * 10²³ atoms

Explanation:

The formula to apply here is the idea gas law;

PV = nRT where ;

P= pressure of the gas= 1.013 * 10⁵ Pa

V= volume of the gas = 4/3 * 3.14 *0.15³= 0.01414 m³

n= amount of a substance = ?

R= ideal gas constant= 8.314

T= temperature= 293 K

Applying the values to the formula;

PV = nRT

1.013 * 10⁵ * 0.01414 = n * 8.314*293

n= 1.013 * 10⁵ * 0.01414 / 8.314*293

n= 0.588 moles

1 mole = 6.022 * 10²⁷ atoms/ mole

0.588 moles = 0.588 * 6.022 * 10²⁷

N = 3.54 * 10²³ atoms

8 0

2 years ago

After flying for 15 min in a wind blowing 42 km/h at an angle of 19° south of east, an airplane pilot is over a town that is 48

masha68 [24]

Answer:

The speed of the airplane relative to the air is 209.47km/hr

Explanation:

Whenever we are solving a physics problem, it's really useful to start by drawing a diagram of the problem (See picture attached). It will help us visualize the problem better.

Now, we know that the plane flew for an amount of time of 15 minutes. For our dimensions to be the same, we need to turn those 15min to hours, like this:

$15min*\frac{1hr}{60min}=0.25hr$

Once our time is rewritten as hours, we can now calculate the velocity towards north of the plane.

$V=\frac{distance}{time}$

the plane traveled a distance to the north of 48km so the velocity is:

$V=\frac{48km}{0.25hr}$

V=192km/hr j

Now, we can calculate the x and y-components of the velocity of the wind. The problem states that the wind is blowing at 42km/hr at an angle of 19° south of east, so the x and y-components of the velocity of the wind are:

$V_{x}=42km/hr*cos(-19^{o} )=39.71 i$

and

$V_{y}=42km/hr*sin(-19^{o} )=-13.67 j$

So the velocity of the wind can be expressed as a vector as:

$V_{wind}=(39.71i - 13.67j)km/hr$

Once we know this, we can find the velocity of the plane with respect of the wind on x and on y:

$V_{plane x}=V_{plane/wind x}+V_{wind x}$

$V_{plane/wind x}=V_{plane x}-V_{wind x}$

$V_{plane/wind x}=(0-39.71 i)km/hr$

$V_{plane/wind x}= -39.71 i km/hr$

and

$V_{plane y}=V_{plane/wind y}+V_{wind y}$

$V_{plane/wind y}=V_{plane y}-V_{wind y}$

$V_{plane/wind y}=192km/hr j - (- 13.67j)km/hr$

$V_{plane/wind x}= 205.67 j km/hr$

So the velocity of the plane with respect to the wind can be rewritten as:

$V_{plane/wind x}= (-39.71i + 205.67 j) km/hr$

Since the problem asks us to find the speed of the plane with respect to the wind, this means that we need to find the magnitude of the velocity, since the speed is a scalar defined to be the magnitude of the velocity.

so:

$speed=\sqrt{(-39.71)^{2}+(205.67)^{2} }$

speed= 209.47 km/hr

Therefore, the speed of the airplane relative to the air is 209.47km/hr

6 0

3 years ago

a copper rod is sliding on two conducting rails that make an angle of 18 with respect to each other, as in the drawing. The rod

gregori [183]

14 because the horses name is friday and sprite cranberry is coming out with a new jersey

6 0

2 years ago

Set local ground level to 700 ft, and record the inches of mercury.

irakobra [83]

The main way in which an altimeter measures the altitude of an object is by calculating the location's air pressure.

<h3>What is an Altimeter?</h3>

This refers to the instrument that is used to measure the altitude of an object when it is at a fixed level.

Hence, we can see that an altimeter should NOT be confused with a barometer, because although they both measure pressure, a barometer calculates the change in air pressure and elevation based on available weather.

Please note that your question is incomplete so I gave you a general overview to help you get a better understanding of the concept.